I'm really confused by that statement. Are they changing the pronouns or not?
Sounds to me like they want Levy to change her book.
The fact is we have no way of knowing which of the options available today Barry would have taken - simply be a female doctor (maybe in the military, maybe gender nonconforming), or be a transman (maybe a doctor, maybe in the military, maybe not).
Forcing an author to change their fictionalised narrative sets a bad precedent.