I think T's sometimes may think that too much information might worry us or scare us. But, for me, I NEED to understand. I NEED information. I supplement my sessions with a ton of reading.

Now, that may not work for everyone but I'd say that if it is important to you, don't let your T sidestep the question.

With a diagnosis, you would be able to understand your behaviors better and would be able to reach out to others with a similar condition.

If it were known that you did not have BP, then you could relax and investigate with your T other ways of understanding your condition.

When I suspected I might have a certain diagnostic condition (based on what a friend of mine was convinced I had and she is a trained T) and then I discussed it with my own T and she said I did not. It helped me a lot to move myself away from thinking that theory was my problem.

And if you don't trust his answer, tell him that. Honesty is the best way to interact with our T's. Whether he is trustworthy or not, your lack of trust will be a signal to some stuff that's going on in your life.