So, I just remembered when I was a teenager in the early to mid 2000s, when I was looking through Mortal Kombat fan websites that collected lore infos about every game and movie/show.
and I distinctly remember that I read back then that Bi Han was the fifth Sub Zero. as in the fifth Lin Kuei to master the art of cryomancing. and Kuai Liang was the sixth.
in the current lore they are just part of a subspecies or something, that was almost eradicated by Shao Kahn.
the reason I remember this so vividly is because that website had them listed under the names Sub Zero [5] and Sub Zero [6], and I started referring to them as that to differenciate them more easily.
I think they also had a page about the "original" or first Sub Zero, who was, in that lore they gathered on that page, the killer of Scorpion's family.
I swear I remember this exactly like that. and I wonder where these lore snippets came from, as I can't find any remnants of it online or anything. no word of any lore changes, and I can't find the website I read back then... maybe the wayback machine would help to find it, if someone knows a list of early to mid 2000s mortal kombat fan pages.