For folks like me who don't know every niche acronym, TAS means "tool-assisted speedrun". That is, a mod took control of the player character.

Reading the FAQ from reddit, Zaspar took a few years to script the playthrough.

Interesting idea. I'm more excited about regular human speedrunners playing on random seeds. Still, I think this probably establishes something close to a lower bound on what's possible. Given that Zaspar has also won in 1h18m (playing normally), it's impressive how close human speedrunners are to the "ideal" preprogrammed player.