My understanding is that PFF tries to identify measurable things that they have correlated with winning and not winning football. Then they assemble the player grade based on the number of measurable things that a player does.
The problem is that just because a player is doing the things they like and not doing the things they don't like, it doesn't mean that this particular player is helping the team win football games, at least to the level that the PFF grades indicate with a sample size of one or two games. There could be a couple good measurables with a lot of bad un-measurables. The single game ratings should always be taken with a large dose of skepticism. Over the course of a season, they usually start to make a little more sense, but even then, the stuff is just correlated with wins, it doesn't mean that doing those things leads to 100% winning.
Generally pretty happy with Conklin though.
Browns left tackle Jedrick Wills playfully mocks PFF’s offensive line grading
brownswire.usatoday.com
I'm sure their agents are out there encouraging them to do things that lead to higher PFF grades.