I disagree, because I've placed A-potential players on my team and they didn't develop. One, a QB, took 5 seasons before I could even consider that player ready to start. That's not a 90 overall QB, that's a QB of 82 overall rating. Potential is no guarantee that they WILL reach high ratings, only that they can.
If you give me a choice between a 75 overall B potential LB and a 60 overall A potential LB, then I'm going to lean towards the B potential player. He'll still reach a solid rating, and he'll get there sooner and be ready to contribute. If I need a LB to contribute now, I need to make sure I scout the right player. If I have the luxury of a deep LB corp, then maybe I can afford to snatch that A potential player and let him develop.
But do I want to spend a first round draft pick on a player who's going to take 4 years to develop? I need my first and second rounders to contribute early. Scouting still comes into play. Maybe there's an A potential player that I can pick up in the 4th round (a project type player) who I can put on special teams and let him grow. But I need to know this stuff ahead of time (unless you're cheating and using the excel sheet that shows draft classes).