These very much tend to strongly correlate. You're definitely more confident in negotiating and counter-offering if you have 10x skill as your leverage.
That’s not at all the case. Five of us recently moved internally via a remapping and they gave us pay rises. I negotiated 15% more than the initial offer, everyone else took the initial offer. Roughly same ability.
Indeed the only reason I could do this was because the new salary ranges were shown thanks to pay transparency.
I would speculate that 10x devs' underestimation primarily concerns their percentile ranking relative to peers, not necessarily their absolute skill. Comparing yourself to the likes of Carmack and Wozniak is what pushes you to become cracked in the first place.