I've never been faced with this problem personally, but what I can say that is that if you've known someone for any length of time say "Bill" and then one day "Bill" wants to be called "Jill" there is an ask that extends far beyond what is ordinarily reasonable.
That's why I think "deadnaming" is totally stupid. That name isn't dead. You just don't like/prefer it. But it was there and people know that name. They know you—and you just changed your mind. That's not their problem—that's yours.