One way to look at it is that 1) they are working for you; 2) they don't know you from a hole a hole in the ground; and 3) there are professional ethics that they "should" adhere to. So on all three counts there is no reason why not to speak our mind, gauge their reactions and knowledge base and then later decide if you feel like trying it another appointment.
Most likely the first appointment will be much more of an intake type interview to get a feel for you, your background, current personal circumstances, and just a tad of hat you're hoping to accomplish with therapy.
If you have a ton of other issues you feel need to helped with you can just start with that and in time get to the core trans stuff.
My goal for starting therapy was to help me with the galaxy of issues I have as a result of being trans and hopefully learn a few tricks on how to fix them. I wasn't looking for a therapist for transitioning, just one that actually knew something about trans people.
As you alluded getting started on HRT is not a difficult process. Doing it the "proper" way requires that you follow some very well intentioned processes. Most times health care professionals do try to act in your best interests.
