Both muscular body types and twinks can appeal to women, it's all about presentation. Jock straps and briefs hold overwhelmingly homo appeal. As well as any kind of flexing or macho posturing. Women into anime like their men in more feminized clothing (like panties or skirts) and more subtle displays of sexuality. Free! got away with this because of the swimming setting and how it wasn't intentionally sexual on the characters' end.