Gao Yang really didn't care much about whether he could drink or not. After all, it was just drinking, nothing worth competing over so seriously.
Gao Yang didn't care, but Glolov did, and although Li Jinfang originally didn't care, after hearing Glolov's advice, he started to take it seriously as well.
Gao Yang felt that competing with a Russian over drinking was unreliable, especially since one of them was nicknamed "Barrel." If one couldn't deduce the implications behind that nickname, that would be foolish.
Samuel could undoubtedly hold his liquor, but Gao Yang had no clue about Li Jinfang's capacity. Although he had heard from Glolov that Li Jinfang could drink well, he lacked a direct understanding of just how much he could actually consume.