I think he knows that, but it measures your absolute accuracy, whereas hitting notes somewhere within the hitarea does not, only whether it's a hit or not based on CS, while this aim aspect could also be measured in an absolute way (regardless of CS, just like UR doesn't care for OD) if we wanted to go down that direction: hit distance from 1x1 centre of hitcircle, averaged similarly to unstable rate (and similarly to hit timing, more than X aim error = miss, where X depends on CS/OD).
It seems fair just like basing acc on UR, but I don't think it'd "feel good" to play like this (even though it'd be good to have mods that allow players to push their "aim accuracy" too by allowing CS7 and stuff like that on ranked maps). Probably measuring absolute error instead of categories wouldn't feel that harsh when applied to accuracy, maybe because that's already divided into 4 outcomes vs hit/miss of aim and we already have OD10-11 that require you to be rather precise with your acc, while CS7< is pretty rare.