You can't look at it that way. PFF doesn't have a cutoff like school grade like 90 and above is an A. They state they grade each position group differently. Also, for offensive linemen they grade pass blocking separate from run blocking. You have to compare players against others in the same...
It's not nonsense … necessarily. The thing about OL, it takes all 5 to grade high, at the same time, or it becomes a schit storm. When they're as inconsistent as they've shown, how often do you think that happens?