If true, why hasn't he won the USO?
Nadal's forehand is not varied. 90% of the time it's a loop to the backhand or middle of the court. When there's a more than obvious opening, he'll go for a winner.
LOLWUT?
Nadal's forehand can create absolute sick angles and on natural courts it is a terrific mix of spin and pace, Roddick described it as the heaviest ball on tour to have on your strings. He prefers the BH side because it is his natural crosscourt swing, because he is a lefty, and he is a known BH abuser as most guys on tour have worse BH than FH. See how he straight setted one of the best BH on tour, Murray, at WB this year and how he keeps a lot of players pinned in that corner only to go for the DTL shot after.
He hasn't won USO because his shots sit up on this court and this can be exploited by ballbashers. Because of this Nadal is almost always put on the defense and you can't win USO defending. On natural surfaces, because of his fh mostly, Nadal keeps his opponents moving around just as much as him if not more. Not the case here.