Much rarer

I agreed with you as far as this. As for the rest it seems unlikely that our genetics implement a complete jump from male desiring to female desiring with no grey area (sweet spot?) in between.

So he's been out as bisexual for twenty years, slept with dozens of women and dozens of men in that time, is currently sleeping with four different women and showing every sign of enjoying it lots, and you think he's 100% gay? Are you sure your beliefs about this are paying rent?

So why is bisexuality so common in women? Why don't you think female bisexuals are lesbians in denial, or under duress to sleep with women? I just don't see how women who have sex with both men and women enjoy it but men who have sex with both men and women are clearly just keeping up appearances.