I would never revert backwards either. If he's doing it for you fantastic! Keep doing whatever it is you are doing. If she wants him in diapers at home then he gets put in one just before leaving your house and she can keep him in them until she sees fit.

I get that she wants him to do it at home and for her, but why make your child go backwards??? I have a little here who is the opposite...will do it at home but refuses to even try here...so she stays in diapers here until she is ready to do it here and at home she is in underwear...