Being fat is a factor. If Tellez is a 100 wRC+ guy in the majors because he lacks the bat speed to hit elite fastballs, then yeah, he is essentially a NP. He can't play anywhere but 1B, and he reportedly is average at best with the glove. I really couldn't tell you if average fastball velo is better in the AFL than it is in AA, but perhaps it is. I wouldn't be so dismissive of reports from these prospect rankers, they watch a lot of MiLB ABs.