@karmi i noticed that too. i came to three different possible conclusions.
A.) the cover here is for a novel, and the manhwa artist decided fuck that sissy nonsense and drew a GIANT MAN instead of the authors intended Edgy Mc'Heroman.
B.) it's a bait and switch intended to fool us into reading this batshit crazy webtoon expecting regular "modern cultivator" or "system in an apocalypse" tropes only to get clotheslined by the korean sword hulk.
C.) this wasn't supposed to happen. the author was making shit up as he went along, (as is the case for 99% of serialized manhwa/webnovel content that doesn't have a prior source) and /intended/ for this to be more generic, but pivoted dramatically at some point to turn the mc into a muscle-god murder king.
option D is baldfaced incompetence/lack of communication between the cover artist and the actual manhwa artist, but i can't believe there isn't some deeper reason behind this incongruity.