I wouldn't say so.
I can give many examples of quiet boring BLs that start with a sex scene. A sex scene in the beginning is a marketing trick to hook the audience to the smut and the art, not focussing on the plot and the characters. Most successful BLs I know don't reveal their card on the first chapter, instead, they give us expectations and hopes for a good plot, hot sex scenes, beautiful art, interesting charecters and more.
well from my own experiences and what i’ve read personally, that’s how the case is. of course i’m sure it’s not exactly 100% of EVERY BL, just the ones i’ve seen. so i will also agree with u
I have a firm belief that if the uke has that black hair style
Their ass is done
this one right here
when she/he speaks fluent facts
i have a very solid 100% belief system that if a BL’s first chapter starts out with a sex scene right off the bat, the rest of the story is going to be
i m m a c u l e n t