While my particular thumb can move that sucker fast--setting Acceleration just-right--to a Point-X, I can see that there's little thumb-memory of the sort you describe; I'd have also to eye-radar to X, in a trice, (another step). Tested: if you put some small squares or circles on a blank page, have to hit some sequence of these to do chores such as you describe.. the ∑-delays are indeed Additive. Rats!

IT-tragedy: a theory killed with a fact. (Though, unless disabled-thumb-workings), the savings of shoulders and such does seem an authentic factor (for those not forever dwelling in Mudbrick Tech Inc.) Solution: have both, eh? Have seen work-spaces so equipped. Dunno their reasoning ... unless ambidextrous? ..Hmmm: wins contest.

Added to listicle: Nothing is ever 'simple'.