Looks like I have been pwned; thanks for pointing that out. Guess there was a reason that no good footnote existed in my memory for the origin of the anecdote.

Part of what stuck out to me, though, was that the anecdote aligned with my personal experiences of things that were once difficult until I ended up having to do them everyday for one reason or another.

But you're right, that's still a far way off from there being some actual study or otherwise repeatable exercise to show this in a clinical setting for learning new skills.