In my "guesswork"...

It appears to me that PB ratings are not used at all in the game - just as the manual says.

What is used is the ACTUAL stats for the player and those can be quite different from the PB stats.

A guy with a defensive PB rating of 1 may actually be a super defensive player. Perhaps the PB value figures in innings at the position...I haven't been able to make sense of that.

My advice - ignore the PB stats and look at the players ACTUAL FPCT, ACTUAL dp's / Innings, actual Assists/Inn, etc. It might not hurt to look at the zone rating because it would be hard to imagine that is not used in some way, but I perhaps that just adds confustion.

I'll take a range 1 player who had 6 assists in 12 innings over a range 7 player who had fewer assists per inning.