The issue isn't mechanics, and certainly not arm strength, which is excellent. It's accuracy and the fact that he doesn't seem to even make one read on many of his passes. It looks like he has one receiver on a given play that he knows he's supposed to throw to, and he launches the ball in that direction no matter how well they're covered. My overriding thought watching the highlights of that game a couple pages back was 'if he regularly makes throws like that, how does he not get picked off all time?' I think his TD/INT ratio has people convinced that he's a better passer than he is... then again, I could be dead wrong. I've only watched a highlight video of one game, and I probably shouldn't be trying to draw a lot of conclusions from it.
With all that said, I don't want anyone to misunderstand me. I think Armstrong is a great QB prospect. I hope he redshirts and works on learning the offense, getting through reads, and throwing some touch passes. If he puts in the work he has the physical tools to be excellent.