That's probably a reason why you can't unlink and it takes you back to the login page -- they aren't synced up..
Yes, and this is an obvious over-simplification, but it is like they decided on how to sync accounts, tested it internally and it was all great. But didn't have someone afterwards go "Good, now do it 'wrong'. Let's see what happens"
Statistically with millions of people getting their hands on this new wrinkle some were going to inadvertently do something out of the pre-determined "correct" order. And here we are, waiting to see if we are going to lose all entitlements and progress after spending at least $100 on the game.