After the reviews of the iPad Air 2 and iPad mini 3 trickled out yesterday, the meme on Twitter seemed to be “Apple needs to create better iPad apps.” Nilay Patel of The Verge said it, @Lessian said it, and earlier @Monkbent said it.

While I agree with their intent—that iOS, now running on 64-bit processors, is fully capable of much more than apps do today—phrasing it in terms only of the iPad does a disservice to Apple, to UX designers, to developers, and to businesses.

I’m here to warn you today that there is no such thing as an iPad app. And if you think about it that way (thinking that iPhone and iPad—and even Mac OS X—apps are different things), then you haven’t fully grasped where Apple is moving to in the future.

It’s funny: in the past six months, the argument has completely inverted. Earlier this year, at a mobility conference, I gave a presentation called “You Can’t Ignore the Tablet”. Now, six months later, here I am warning people not to create iPad-only apps.

There are both technical and non-technical reasons why iPad-only apps don’t make sense. Here’s a list of 4 reasons why you don’t want to create an iPad-only app.

1. Every Apple iOS app is universal.

Look at every app Apple makes, both built-in to iOS as well as separately-downloadable apps like Pages, Keynote, iMovie, GarageBand, and even iTunes U. If there’s an iPad app that Apple makes, it also runs on the iPhone.

And we’re not talking about a “cut-down” version running on the iPhone. Every iPad app that Apple makes runs with the exact same feature set on the iPhone. Yes, even productivity apps like Pages, Numbers, and Keynote have the exact same features on the iPhone. Go ahead, try them out, I’ll wait.

Use a complex app such as GarageBand or iTunes U on an iPad, and you may wonder how they work identically on an iPhone. Really, it’s just the navigation and toolbars that change—it’s a challenge to UX designers, but one that can be done (see my Mobile March presentation for ideas on how product managers and UX designers should plan for both phones and tablets; it was written before iOS 8 simplified things, but still contains much useful information and background).

2. Do we talk about Mac Pro apps vs. MacBook Air apps?

Of course not. Every OS X app runs on every size Mac, whether that’s a Mac Pro with dual 30-inch screens or a MacBook Air with an 11-inch or 13-inch screen. Yes, even Final Cut Pro X and Adobe Photoshop.

So why the iPhone/iPad dichotomy? Why would you think of an “iPhone app” and an “iPad app” being different things, if you don’t think of a “Mac Pro app” and a “MacBook Air app” being different things? It doesn’t make sense.

@Lessien mentioned that GarageBand doesn’t make much sense on an iPhone. Well, you could say the same thing about Final Cut Pro X or Photoshop on a MacBook Air. There’s a difference between optimal use vs acceptable use. GarageBand on an iPhone is no less usable than Photoshop on a MacBook Air. Neither one is optimal, of course, but how many users are you going to lose if they can’t use your app on the go, whether “on the go” means an iPhone or a MacBook Air?

3. The iPhone 6+ Changes the Game.

In the early days of iPhones and iPads, I can see how you might have thought that iPhone apps and iPad apps were different things. After all, Apple made it technically possible to target apps for one or the other, or both (in Xcode, you can create iPhone- or iPad-only apps, as well as Universal apps that run on both). Apple also had some APIs that ran only on the iPad (things like split screen views, half-screen modal windows, and popovers). And iPhones had 3.5” screens while iPads had 9.7” screens. Big difference.

But that’s been slowly changing. iPhones went from 3.5-inch screens to 4-inch, and then to 4.7-inch and 5.5-inch screens. Meanwhile, the iPad mini dropped down to a 7.9-inch screen.

Then the iPhone 6+ with iOS 8 debuted, and put the nail in the coffin of the “iPad app” vs. “iPhone app” debate. Without getting into the technical whys-and-hows, new iPhone APIs in iOS 8 mean that all APIs that were iPad-only now also work on iPhones. There simply is no difference anymore.

And, really, how do you design a great iPhone 6+ app without incorporating features of the iPad, like split-screen views? You can’t. I mentioned earlier how all Apple iPad apps work identically on the iPhone. There is one exception: the iTunes U app recently added the ability to create courses on the iPad—but this was before iOS 8 debuted. My guess is the next major update to the iTunes U app will add support for creating courses on the iPhone, and require iOS 8.

Looking to the future, what’s to stop the iPhone from continually growing… to 6 inches and beyond for the iPhone 7? Users want choice in iOS device size, just like they have a choice in Mac size. You have to plan for your app working on different sized devices, not just phones or just tablets that you use or prefer.

4. iWork Proves that iOS Apps are Powerful Enough to be OS X-Style Apps.

As if the iPhone 6+ wasn’t enough evidence for all iOS apps being universal and running on iPhones and iPads, there’s one more clincher:

Not only are iPhones powerful enough to run iPad apps, they’re powerful enough to run OS X (Mac)-level apps, too.

Remember a year ago when Apple introduced the first iPad Air and iPad mini 2 (Retina)? At the same time, they discontinued the iWork ’09 apps for the Mac (OS X), with much nail-biting by users ensuing. In its stead, they released brand new iWork apps for OS X that were exactly the same as their iOS app counterparts.

Think about that for a second. Pages, Numbers, and Keynote work exactly the same on iPhones as they do on iPads as they do on MacBook Airs as they do on Mac Pros. (Intel, are you worried yet?)

Sure, the user experience is slightly different, taking into account keyboards and mice on OS X, and touch screens on iOS. But the functionality is the same, and even the file formats are identical.

Remember, Apple’s A7, A8, and A8X chips in iPhones and iPads are “desktop class” 64-bit processors (http://www.cnet.com/news/apples-a7-chip-makes-a-run-at-intel/#!). And while iOS and OS X react to user input differently, they are based on the same OS foundation. It’s not difficult to write apps using Xcode that share fundamental business logic, and just have a different UI on iOS and OS X. If developers can make apps that run on everything from iPhones to Mac Pro’s, why distinguish between iPhone apps and iPad apps? That’s just silly.

Yes, Apple needs to encourage more sophisticated iOS apps—and I’m sure there are some gestating right now in Apple’s labs (Photos app, Final Cut Pro app?). But don’t call them iPad apps.

The next time someone talks about “iPad apps” or “iPhone apps”, gently remind them that there are no “Mac Pro apps” or “MacBook Air apps”. Make sure your apps support all devices. There are only iOS apps and OS X apps—and as iWork proves, even that distinction is blurring.