To be fair tho this is the average conversation bi people be having with their first gay/lesbian partners. MLM/WLW are usually more ready to disqualified you as "not gay enough" or "not rlly gay" way more often then they should
At first I thought the same thing as you do but in retrospective maybe it was more Jaehyuk's point of view rather than the author erasing bisexuality from their world, maybe I'm giving them too much credits but it doesn't feel so out of place for a character like that to not know a lot about the queer community.
hmmm when youre bi, you're into both. atp Jaehyuk is no longer interested to women and now only to Garam alone that's why he now identifies as gay. Your past relationships doesnt justify or add up to your current sexual orientation.
why do authors always forget bisexuality exists and shouldn't garam, who is gay and a member of LGBTQ+ know about how jaehyuk's prolly bi and point it out instead of this "not really gay!" bs