Doesn’t matter what kind of males these men are into, those men are still bisexual. The fact that they continued to find you attractive even after you explained to them you’re not trans and not effeminate is proof that those men are bi. The men don’t have to be open about their orientation, but they are on Grindr looking for males, so obviously they’re not straight. And yes, it’s okay to be attracted only to certain kinds of men. I’m not attracted to effeminate men, those men who are hitting you up are not attracted to masculine men, we all have our preferences and we shouldn’t be ashamed to declare them.

If these "straight" men keep pursuing you, don’t be afraid to keep the conversation going with them. You don’t have to date them or anything, but talking to them can help them to make sense of their own orientations and realise that men can also have long hair. Not only would this help them, it would also help any potential sons of these men who might be effeminate or bisexual, or both. This could prevent a future trans kid down the line. And if one of these men end up coming out as bisexual, you could say that you helped him, and subliminally, the male bisexual community in general.