Look, the very link OP has posted even has an image which shows that the handspan of the "internationally acclaimed pianists", it is wholly concentrated in above average handsizes. Which only a fairly small portion of the population has.

http://smallpianokeyboards.org/wp-content/uploads/2019/02/Ri...

Never "small". If we are talking about "greats" it's even more so. You can't be with a small hand span.

Not sure what kind of more evidence you need.