The only thing I can say for sure about Allar is that he has a very strong arm. Unfortunately, arm strength is about the 10th most important thing you need to be a great QB.
He might end up being a great QB. I hope he does. But the hype you hear from the announcers on TV is way overblown. High recruiting ranking and rocket arm give them massive boners. But will he have the pocket presence, accuracy, decision making ability, and the ability to quickly find the open man? Remains to be seen.
I think he's shown a lot more than that. He steps up, and has shown, good pocket presence. He's shown that he can run well enough to compliment the position. He's shown he can command the team in a challenging environment (Purdue when SC got hurt). he's shown he can deliver the ball on the run. He's shown he is willing to finesse a throw (put air under it).
His decision making is still to be tested. Can he process receivers in real time? Can he read defenses? What is his accuracy for short, medium and long throws? Those, and more, we don't know yet. But a lot of that is coaching. And what he does have cannot be coached. No coach is going to give him that strong arm, make them 6-5, and more.
Lastly, that strong arm is more than just fun. it allows him to deliver the ball, on a rope, running to his left or right. It also allows him to throw a deep-out pattern without fear of it being picked off. These skills require the D to cover more of the field for longer. It is why, if you want to be a starter in the NFL, you have to show a strong arm at the combine. Trace and McGloin would be very good NFL QBs, if they had strong arms. Colt McCoy as well. They just don't have the arm strength to make all the throws and put pressure on the D to cover all layers of the field.