You're spot on for my case, but I think it holds true more often than not. Sure, there will be exceptions (in terms of individuals and specific boulder problems), but generally, finger strength appears to be the limiting factor, at least for climbers who I know. Those with stronger fingers than me usually climb harder, and those with weaker fingers usually climb less hard.
At the top level there's Giuliano Cameroni who bouldered 8C+ before he could do a one arm pullup. I bet every 8C+ ascensionist could hang an edge with one arm though! Consider an imaginary person who has never climbed before, and they have average athleticism, coordination, etc., but for some reason they can 1 arm a Lattice rung. I bet they could climb 8A within a year!
Maybe i'm way off on all this but i'm just saying what I see!
Note: i'm purposely sticking to bouldering here as I don't know anything about the territory that comes after 10 moves!
