I'm not sure why he would do this....but like you said at least he doesn't want to hide anything.
I will say this is my biggest fear if I ever have the chance of telling a man. I am in the same opinion as you, I want to just be a normal girlfriend....not his trans girlfriend.
The same goes with being up front with a man, this is why I am not telling them right off....or even after awhile (not good). They are attracted to me as a women, not a trans women.
Ugh I'm so lonely, and the one man I was intimate with had brought me so much joy, I want (need) to experience that more. It had been many years before him, and now I am not use to being alone. Funny it didn't bother me this much the 8 years prior.
I hope everything goes good, I am sure once his friends see you and talk with you they will se nothing other than a women!!!

:)Just be strong and don't overthink things when meeting them....I can offer this advice, but frankly I have a hard time doing it myself.