I say that the logic behind your conclusion is poor. The expert might think that Pete is more complete than Rafael overall, even though his backhand is not better.
Something like this: Sampras, like Nadal, has a tier I forehand/movement/mentality, and, unlike Nadal, a tier I serve and a tier I net game. Neither of their backhands are tier I backhands, and therefore mediocre/weaknesses in the context of the thread where the quotes is taken from. Ergo, Sampras is more complete than Rafa, but not because of the better backhand - the expert might actually think that Nadal has the edge in that department.
