Does Tomoaki actually prefer tomboy looks? The story so far hasn't indicated that in any way, almost the contrary since he doesn't particularly get mesmerised by Iburi in the way of attraction. He admires her coolness, but that hasn't got anything to do with being attracted to her. Yet Ibuki here does act like she assumes Tomoaki would be affected by her 100% male style. We should assume at this point this male style is what Ibuki herself prefers, otherwise she likely wouldn't keep doing it. She doesn't look so weak-willed she would believe she must do it because "she's not cute or feminine and people would hate it if she tried to dress as if she was."