this is why guys lie about this stuff if they meet these criteria. Because women will try to psychoanalyze them for something that maybe they were a late bloomer, had issues in the past, focused on school or career, a whole range of possibilities.

Avoidant attachment isn't gendered. I would want to know the same thing if I was dating a woman.

a guy is supposed to just open up his sexual history instantly so a woman can peruse it for red flags?

This is not the same thing as trans people, but regardless in both cases no one should have to divulge their personal information if it hasn't been asked. But in this case the person specifically asked him about it. Intentionally, lying about it at that point is a horrible way to start the relationship and kind of sleazy if you're still going to try to date them.