Maybe we just have different definitions. A fk buddy is for me a guy you only have sex with and maybe watch a movie now and then, someone you don't care especially for. I want to go out with him, cook with him, talk with him, have sex with him and so on. I care for him, I find him fascinating and interesting. I just don't want to tilt into a relationship where we see each other more than about two times a week. My last relationship ended because it went way to fast. We practically lived together after a month... I need my space.
I would not call it "lead him on", because, well, when you date someone (or whatever to call it), is it a promise of something more? Of course, if you see each other often or in a long period of time, thats something else. And it is naturally to have the conversation about "us". I would talk about it before that. I'm pretty sure that IF I find out that he is attracted to me too and IF we are intimate, that he wouldn't think of me as his girlfriend automatically. If I kiss a guy I don't go: ooooh, we are going to get married! It is so different what people things. Or what do you think I should do?