Yes! I can so relate to that! But it went a bit the other way around in my case.
Former T knew everything about my did. Although I have been denying it for a long time, I really absorbed everything she said about it, had it processed in different stages, and now, well, I've accepted it and that makes things so much easier. But I had to quit her because I could not afford to see her anymore. I could get another T via insurance, which is a lot cheaper, probably good too, but he doesn't know a lot about did, I'm his first patient with it. So yes, I have to explain so much, and now I even feel like I have to defend myself on it - like he doesn't really believe me.
It may sound strange, but I feel like I'm outsmarting him... which definitely is not a good feeling in therapy.
Good question, thank you. Makes me realise that this whole new therapy is actually quite useless.