IRL if you have gay sex it only makes you gay if you find you like it and decide to identify as gay.

If you are a man and identify as bi, then no-one mainstream will want to date you and if you're a woman and identify as bi, lesbians will be spooked but straight guys will fetishize you.

So you may want to identify as gay but exploring your straight side sometimes. Challenging your position on the Kinsey scale, as it were

According to Russel T Davies (and the series Bob & June which examines the idea) gay as an identity doesn't necessarily correspond to behavior, which is how I've ended up in Lesbian culture while possessing male characteristics. (disclosure: I've been married to a lesbian for twelve years during which I re-identified as enby and renounced my manhood. It's a long story.)

That said, the blood banks used to exclude men from donating if they ever had sex with another man, even once, what is a permanent exclusion where people who pay for sex are good after a year. I think this restriction is lifted now, but it was there for decades, including when I was donating plasma. So at least according to the California Pacific Blood Banks, a single intimate moment with another male hottie is enough to mark you as gay forever.

For every other part of LGBT+ -adjacent society, though, meh.