Genuine question here.
What is "player skill"?
Like...what is it, what is the thing that is happening when one is displaying it? What is the thing one acquires by attempting it and failing to display it? What is gained through it?
Because every time I've asked someone to explain the difference to me, every time I've tried to dig past the frankly tedious nondescriptive rhetoric, it either goes nowhere, or seems to end up being really not very much different from the other kinds of things that other games do.
Player skill is when the majority of the solution is derived from elements not intrinsic of the character's elements nor the standard usage of those elements.
Pilot vs plane.
The OSR mostly relies on players solving problems or dealing with obstacles via elements outside their characters or using their character abilities and equipment in unexpected ways.
That's why I say it's lower power and low customization as core elements. Because once you can brute force problems away with magic, it stops feeling like OSR.