I merely used PER as a guideline. PER doesn't measure defense, which is more important than offense for a center (specifically, post offense). It just so happens a lot of centers (Tyson Chandler mold) are elite pick and roll finishers.
My personal PG ratings
95 (+5) Chris Paul (LAC, 26.0 PER)
94 (-1) Stephen Curry (GSW, 28.0 PER)
91 (-3) Russell Westbrook (OKC, 29.1 PER)
90 (+3) John Wall (WAS, 19.9 PER)
89 (+1) Kyrie Irving (CLE, 21.5 PER)
87 (+10) George Hill (IND, 21.5 PER)
87 (+2) Damian Lillard (POR, 20.7 PER)
87 (+2) Jeff Teague (ATL, 20.6 PER)
85 (NC) Kyle Lowry (TOR, 19.3 PER)
85 (-1) Mike Conley (MEM, 18.6 PER)
85 (+4) Ty Lawson (HOU, 18.5 PER)
84 (+3) Brandon Jennings (DET, 19.7 PER)
84 (+4) Jrue Holiday (NOP, 18.8 PER)
84 (+1) Eric Bledsoe (PHX, 18.4 PER)
84 (+4) Darren Collison (SAC, 17.5 PER)
83 (+2) Kemba Walker (CHA, 17.6 PER)
83 (+5) Reggie Jackson (DET, 17.2 PER)
82 (+1) Isaiah Thomas (BOS, 20.6 PER)
82 (-2) Tony Parker (SAS, 15.9 PER)
82 (-2) Derrick Rose (CHI, 15.9 PER)
There are few PGs who substantially impact a game defensively, so there isn't much PER noise. Each other position has defensive specialists but for PGs it's pretty smooth sailing from the top down.