It’s the same finger position for zero and okay, but I’ve never seen anyone do “okay” without also moving their hand forward too. Kind of like how the letter Y and the word yellow are the same finger positions in ASL, but yellow involves movement that Y doesn’t.
My brain doesn’t recognize there as being a hand sign for zero. To me the version with fingers extended is ‘okay’, and the version with fingers closed is some weird sign language symbol I don’t know because I don’t know sign language? Or maybe it’s a baseball signal? I dunno.
I actually remember in my part of the US (Chicago) being jokingly told that the OK sign stands for “asshole” back in the 80s. It was explained as spelling out as A-S-S (pinky-ring-middle finger) and “hole” (the thumb and forefinger “hole” you make in the OK sign.) The area being a mish-mash of ethnicities and cultures, I suppose it was borrowed from one of these cultures and then somebody retrofitted it with an English explanation.