The bottom/uke is most often the character from whose perspective we are given. Most times it starts with the bottom's pov and we dont get the top"s pov until later (if at all). So even when the pov l is split, its the bottoms pov that is told first so they're the main character.
There are few BL manga/manhwa that are primarily told from the top's pov, which is likely because authors/artists of BL are primarily women. I'm sure there are lists for manga with top mcs tho, where the top/seme is the mc. For example, commenters under To You At Dawn are currently having difficulty with referring to mc/ml because the top/seme was the first character whose perspective was shown so the top is technically the mc but since we're so used to the bottom being the mc people are confused on how to talk about them

Am i the only one who's confused who's the ML and MC in a BL story? coz like they're both males how am i supposed to know who's the male lead or main character????!!
does it stands for something else?
is there a gender rule I don't know?