I don't think the point is entirely invalid. If CPJ thinks Ty Griffin could be a gamebreaker at A-back this year I don't think him being QB3 would hinder a switch. Having a true freshman as third string hoping for redshirt isn't unprecedented for us and we survived when it happened. You also didn't mention that MJ is a spring practice ahead of where Vad was.
I mean it's not likely by any stretch but you did say there's no way it would happen. I don't know about that.
The point isn't that TG can't be a great AB, even this year, it's that he's #3 QB this year and CPJ isn't going to risk MJ's redshirt to play another reserve somewhere else if #1 or #2 are down. It's obvious that TG is gifted with the ball in his hands...but it's not clear that AB is even an option (no pun intended), he may be a DB or even a WR. We do know for a fact that TG will have to be QB3 this year because CPJ wants to protect MJ's redshirt for development.
The only QB CPJ has recruited to play as a true freshmen was Jaybo Shaw, and that was because it was by necessity. History shows, even with guys that eventually move from QB, that CPJ wants to see how they develop there over a year during a redshirt freshman season (Tevin, Sims, Days, Luallen, Andrews, Vad, JT, Griffin). It's going to be the same with MJ.