Brian Stucki proves that text replacement syncing on iOS is fundamentally a pile of shit (my words), but its made even more odd because:

From my own experience, syncing of all other data via iCloud has really improved. Notes, Calendar, address book, reminders, photos, etc all sync almost instantly across all devices.

I can echo this. iCloud is flawless everywhere except text replacement syncing. My work email shortcut is three @ signs. When I left my old company in 2014 and came to my new one, I swapped out the replacement there. I have to delete the old email every other week, it just keeps showing back up. For no reason.