Actually, look at Tim Tebow. It was clear to everyone he was great for Florida and in college as a QB but never going anywhere in the NFL at that position.
Some offensive schemes teach skills that easily translate to the NFL but Heupel's offense doesn't emphasize qualities NFL teams are looking for in QBs and WRs. It's not a new criticism as it was said about both Hyatt and Tillman concerning running routes.
With criticisms, if you hear it once, perhaps it's a fluke. Twice, you should examine it. More than that, you probably should look at what they're talking about.