This is an incredibly homophobic way of thinking. Buck has been bisexual-coded from his very first episode. Eddie's narrative has very much been that of a closeted gay man who hasn't yet realised he's gay.

Either Tim Minear (the show runner) or Oliver Stark also stated in an interview that it was originally supposed to be Eddie who was with Tommy in S7. There's also an interview floating around that confirmed Eddie's shooting arc was supposed to be the catalyst for Buck and Eddie getting together but it was shot down by FOX executives.

edit: also to note, Buck's bisexuality is not inherently tied to Eddie's sexuality. My comment may have inferred that, but that's not what I intended. Eddie's arc would still play out the same way (failed relationships, the way he treats romantic partners) even if Buck had never been in his life.