...and he edited his comment.

I did. It doesn’t matter what they call themselves. People have been hiding the truth about their feelings, deviations, etc since forever. I fail to see anything relevant here.

Categories are a human-defined thing, not something that is "out there". The point is to try to understand human behavior better, and that includes questioning pre-existing categories, and perhaps, defining new ones?

Quoting the abstract again: "Latent class analysis revealed six distinctive "types" of heterosexually identified students whose last hookup was with a same-sex partner.[...]"

Do we really need to use tax money on this kinda of stuff... Is it not clear that minorities would pretend to belong to the majority. Because it is more benificial?

It's relevant because we have to use terminology like MSM (men who have sex with men) in public health because otherwise we exclude people who do not identify as homosexual or bisexual. Often we don't care how someone self identifies. We do care about things they do.

Knowing why some men identify as heterosexual and refuse to identify as anything else -even though they have sex with men- can tell us about stigma and discrimination and can help us provide healthcare.

https://en.wikipedia.org/wiki/Men_who_have_sex_with_men