This loses the plot. Futa are women with a dick. Testicles does not make the thing more gay or not, the fetish is of a woman with a dick. By trying to rationalize it with real world logic you are losing what makes it a fetish. No one is like "I can't jerk off to a futa with balls because that's biologically a man," because in fantasy things can work without making real world sense. Some people don't like futa with balls but it's not because they think that they are men, they just don't like balls on their futas, and that's okay.
It's not reductionism that led to the word being packed together, it's that futa has always referred to most if not all of them (Just a dick is the rarest one and I've literally never seen it before, mental images of it gross me out though) and the subcategories were people trying to be super specific when that isn't necessary for the average person. Most people when looking for futa want the fetish as a whole and will just pare down the stuff they don't like. I don't like trans content but don't mind a futa with dick and balls. Most artists understand this and don't conflate them, in fact I remember a doujin from over a decade ago where an international fuckfest competition was happening between futas with balls and the ones from Brazil were disqualified for not being futas but secretly trans. Damn that was silly.
Why would you have to be bi to enjoy futa? Adding a dick really doesn't change the fact that it's a woman, and just because you like a dick on a woman doesn't mean you like dicks in general. In my previous comment I talked about the gross shit that is cuntboys. Logically because they are in the same vein as futas that would mean that if you were bisexual or were a little gay you would like them. I have only ever seen women like cuntboys. On the other hand I've seen lesbians like futa as well, even though they don't like men.
Also why even post that futa talk goes on for a long time and then call everyone who likes it partially gay or bi? That's just interaction bait.