Hey, total top here and not at all. We're all different, and there are some things that are very clear to each person from the start and other things that leave room for exploration and self-discovery. I know many pure bottoms who always knew they were so. Before ever kissing a guy or sucking a dick, they were already playing with their ass, sticking things in it and fantasizing about getting fucked. Some tried topping eventually just to confirm what they already knew, which is, that they are bottom.
The exact same thing works for total tops. I never thought about myself being fucked, I don't desire it, my ass is not an erogenous zone for me. My fantasies always involved me sliding my cock in an ass or mouth (mainly ass for that matter, and eventually I confirmed what I always knew, which is that I'm top with a strong urge to fuck raw and breed). A couple of times I tried exploring my ass out of curiosity. My reasoning was "if so many guys are crazy about it, there must be something good to it," but found zero pleasure there. On occasions, guys that I trust and feel comfortable with have asked to rim me and I've let them, but it's for their pleasure as I get nothing out of it. You can think of it similarly to guys who go crazy with nipple or toe play, yet for others those do nothing. Would you call it internalized homophobia or "nipplephobia" if someone doesn't get pleasure from their nipples? As for sucking, I don't particularly enjoy it either, but I'm open to it if I feel comfortable. What I intend to say here is that there was room for exploring on the oral front, even though it's not my preferred thing to do.
In summary, only you yourself can know what you like for sure, what you're not so sure about and what boundaries you can push. I hope this helps.
