It's from a different but similar game. Alfajer's KAST was mostly high 60s before he got signed to Fnatic, now it's consistently high 70s.
This is partially because Alfajer was put on Chamber duty when he was on Surreal, along with KJ/Raze. Not a perfect example but it does help illustrate my point when I say that KAST does not necessarily take into account Agents and utility because that's not in CSGO. I never said it wasn't the best we have rn tho. And I never said it wasn't good-just that it's not as accurate. Which is true.