Im not sure I completely understand your situation. So you are a trans man, in a relationship with (or at least mutual interest in) another man, is that right? If he sees you as a girl, like that person you mentioned suggests, why would he want to be with you in the first place? I dont think that makes sense. If that was the case though, and he wanted you to be his “girlfriend” and look like a girl, then yes, it would probably be transphobic.

Regardless, having a preference for your SOs looks is normal imo, and sometimes it can have significant influence on a relationship. Im not sure how I would react if my wife wanted to get a nose ring for example. I dont like them, I dont like looking at them, I dont know why exactly but its just not for me. But does that make me mysogynistic? If it was important for my wife and her self-expression I would obviously respect that but it would lead to some difficult discussions. I cant control that she would be less physically attractive to me and I would need to tell her that and she would need to make the decision factoring that in. Pressuring her or demanding changes in her looks would be wrong, but not telling her my feelings would be too.

I think you will have to decide between your authentic self-expression and appealing to others. You will need to weigh up how important it is to you, potentially sacrificing a relationship for it, but if its that much of a priority to you then that relationship wasnt meant to be in the first place.