I think you main point stands, but way more men have gay sex than are willing to self-report as gay or bi in a government survey
My experiences point to a lot of bisexual men living in the closet and are ashamed of what they are. I think guys in that situation typically want the heterosexual lifestyle of kids and marriage, but the thrill of sex with a guy on the side. There have been very, very few guys I've seen on there who are married to a woman who are able to openly explore sex with men with their wife's consent.
I can't really comment on women who are bisexual however.
https://slate.com/human-interest/2016/05/over-80-percent-of-...
"The massive 2013 Pew Research LGBT Survey found 84 percent of self-identified bisexuals in committed relationships have a partner of the opposite sex, while only 9 percent are in same-sex relationships"