Very good question!! Im guessing its down to indivdual prefrence and playing style. I know Pavel is influenced by super human shredders such as Rusty Cooley , Michael Angelo Baito, and Michael Romeo to name a few who also opt for the classical position
But then on the flip side of the coin there are awe inspireing shredders such as muris, who hold it on the right leg and definatly have no speed limit !!!
Looking at legendary shredders like Paul Gilbert, Yngqie Malmseen, Vai, Buckethead etc they opt for this pose too.
So Im guessing (and it is a guess) what its all down the style and prefence you go after