Text replacement syncing is completely broken. Sometimes it works, sometimes it doesn’t. Sometimes it will only sync back old snippets that you have deleted. Sometimes the sync will work one direction, but not the other. Every time I ask about this on Twitter, it brings a strong response of similar experiences.
Even though I know it’s broken, I decided to get scientific about it.
Two things: First, this is incredible work; click through and see all the work that went into this. Second, Apple really should fix this feature.
Update: I got a note that this is supposed to be much better with iOS 11 and High Sierra. Fingers crossed!
Update 2: Gruber says that this system is being migrated to the much more reliable CloudKit with an update coming to iOS 11 and High Sierra soon. Good news!