I mean, if you want to bring up PFF's grades on pass blocking with a small sample size, certainly we can bring up Williams' rush per attempt is at 4.2 v.s. 3.0 for Montgomery. I don't put any weight into that, because Williams has only rushed the ball 4 times. But it makes about as much sense as you trusting PFF's grade for pass blocking.
I'm basing my opinion on Williams' pass blocking off of what I seen him produce in college, albeit sparingly as I didn't watch every game, and based on what the coaching staff and Rodgers and others have pointed out during the offseason, and based on what I've seen from Montgomery with my own eyes through the first 3 games. He's almost gotten ARod killed on multiple occasions where he's either failed to pick up a blitzer when he should have (not understanding what his responsibility is), or totally demonstrating a lack of skill to effectively keep the blitzer in question from reaching Rodgers' grill when he does pick it up.
I think if nothing else, Williams needs to see some more action either through getting an entire drive, or by rotating in and out with Montgomery. I don't feel comfortable with Ty's current work load, and again, in a short week, I think it would be the smart move to give Williams more snaps.