Why are BL/Yaoi Authors so Scared of Bisexual Men

Literally the title why tf are there barely any characters who acknowledge they’re bi?? Like imagine… walk with me here… you’re a BL character, you’ve been sleeping with women and seem attracted to them but suddenly you catch a dick and you’re either
A) only gay for you bb (ew, just ew)
B) gay (which is valid but srsly ALL OF YOU? NOT OF U EVER QUESTIONED THE FACT U WERENT INTO PUSSY WHEN U WERE DROWNING IN IT?)
C) actually im straight but i like u ig (no comment on this)
I think this is becoming less of an issue somewhat cuz I see more and more acknowledge they might be bi but idk I feel like it’s smth that always bothers me when im reading
I feel it can sm to a character too, you explore sm with just their sexuality and with biphobia
I think there’s a bunch of closeted bi men who suppress their feelings sm for men and end up with a woman anyways even if they fall for another dude that’s an angst potential
Or you can show that they’re a coward that runs from their feelings
Obv im not expecting super educated or a crazy coming out to the whole family or characters from PORN but I feel like there should be more? It always bothered me
ANYWAYS YEAH IDK WHAT DO YALL THINK?