This is all speculation.
We only have a sample size of 4 players + Bruguera and Sampras.
Nadal hits the most spin out of that, but so what?
At least measure all of the top 200, focusing mainly on clay-courters. I still wanna see RPM data on Andreev forehand. I reckon that wipes Nadal's forehand.
And take an average of forehand AND backhand topspin, cuz guess what - u ain't gonna get forehands 100% of the time.
Nada's backhand lets him down bigtime on spin production.