Yep. PFF treats the game of football as a game of 1 on 1 matchups. Problem is that football isn't a game of 1 on 1 matchups. PFF can reliably tell you who the best players are and who the worst are. Of course, your eyes generally can do the same. But to be fair, I can't watch every game. Where they fail is sorting out the guys in the middle. Because that is where you need to know scheme and assignment. You don't need to know Aaron Donald's assignment when he's blowing up blocking schemes. But for most guys, you do need to know what they're doing (and what they were supposed to do).