There are a lot of reasons people go to therapy, the therapist gives you a diagnosis based on insurance billing codes. They don't have to diagnose you with gender disphoria for you to talk about it . If you explain that you are concern about a gender disphoria diagnosis so early on, they could probably find another diagnosis for billing. This won't necessarily impact your chance to hormone therapy in the future, because there are a large number of places that use informed consent.
If you live in the United States, and are looking for hormone therapy, the primarily prescribed T-block has other uses and if you have one of those conditions, you might be able to access it that way.