I've been following his grades all year, and they seem pretty good and fairly assessed.
It would be interesting to see how he grades veteran QBs using the same system. The trouble with a grading system like this is that it's not totally clear what each grade represents, or if he's taking into account the fact that they are all young and inexperienced -- so, is an A+ for Lamar Jackson the same as for Drew Brees? Or is it adjusted for the fact that he's a second-year QB?
If it's the latter, then it would seem like Lamar probably deserves a higher grade. If it's not, my sense is that Josh probably deserves a slightly lower grade.