Oh, so that's how they solved it...
Minfilia is the questgiver for the start of that chain, so they need to be sure you've gotten her out of the Waking Sands after a certain point so she's not still there after the coup in Ul'dah. Clever. And also why every quest in the known universe post-Heavensward uses a proxy questgiver. Guess that means Urianger has more job security than anyone else in the cast, because that Final Coil unlock makes him bulletproof.
