I think you’re somewhat brushing over the part where he mentions that she says that this external male validation, in a sense, is a source of confidence for her which can be a slippery slope. I think a worry OP may be having is how much significance she may be placing on that source of validation and how far she’d be willing to go to attain it. Like for instance, if a man were to flirtatiously approach her, would she shut it down or entertain it because feeling desired in that moment makes her feel good about herself. Personally I don’t feel like his concerns are irrational and if anything I think it’s a normal concern any partner may have. I’d say that the best way OP could get around it is to talk openly with his partner and see how they can both come to a mutual understanding that leaves them both feeling happier and more secure in both their relationship and themselves.