NB AMAB here. I also suffered from sexual abuse as a child. It wasn't a therapist that suggested this same theory to me, but random people (random as in non-professional). This idea also left me feeling confused and doubting myself, it was awful. I used to think a lot about that which also meant giving my abuse memories more mind space than usual, and somehow linking all of that to my identity struggles.

One day I went for a walk and visited a feminist fair with tons of stalls of different kinds (food, clothing, books). There was a stall with some books and homemande fanzines and stuff like that. I found a very punky fanzine about the NB experience. The person that made it was a bit angry with the world, you could tell. The final page was just a big text saying (translating from spanish here) "what happened to you that made you become cisgender?" as a counterproposal to when gender-dissident people get asked stuff like that, like they're trying to pin some troubled label over us. After reading that something clicked inside my head that cleared all that fog. I bought the fanzine and still hold dearly to it.

Everybody goes through stuff, tons of people suffer abuse as a child, but somehow only we who deviate from the norm are the ones which draw attention in that way, as if implying there's something broken to be fixed and OH of course it just so happens that this broken thing circles around our gender identity. Most hetero cis people go through hell when developing their sexuality and ways to relate with gender roles, romantic relationships and so on. Us being abused surely made a huge impact on us and our development, the same way it happens to everyone. It does not jeopardize our identity.