To answer that question, one must first answer this question: Is it less gay to masturbate to effeminate men than it is to masturbate to burly masculine men?
If the answer is yes, then one might claim that the Part 5 Jojos, while certainly still gay, are considerably less gay than, for example, Part 2. Potentially, even, almost not gay. If Part 5 Jojos are almost not gay, then Part 6 being Part 5 but actually female would make it, in fact, not gay. Almost gay, perhaps, but not gay nonetheless.
However, if one believes that effeminate men are in fact more gay than masculine men, then Part 6 Jojo being essentially Part 5 Jojo with breasts would make it, while potentially less gay, still gay.
Of course, this is all moot if you subscribe to the idea that male and female is a concrete line that denotes gay/not gay, and all other traits are secondary to that.