For me the main thing I can't get over with Fromm is not the arm strength althought I think you can see it in certain situations. The main things I dislike and I think will limit him in the league are:
-pocket presence - it's the worst from anybody in this class. It's horrible. He is statuesque in the pocket and has no feel or vision or ability to even try to avoid rusher unless it's the most obvious of situations, he doesn't step into the pocket, he doesn't sidestep rusher...he would just stay in there and try to deliver the ball from the platform he's initially dropped to.
-inability to playmake - this ties into the pocket presence and armstrenght weaknesses too. Very little ability to make plays out of structure. If the pocket breaks, he's usually done, doesn't escape collapsing pockets and if it's one of the obvious cases where he actually sees it he doesn't have the armstrenght to make plays on the run and off platform.
I love a lot of the other things about him(leadership, accuracy on short to intermediate throws, anticipation, reading the field, smarts and command of the offense at the LOS, adjustments), but in today's NFL when defensive linemen have such athletic freaks and OLines are struggling to protect the QBs, IMO having the ability to navigate the pocket when it's workable or to leave it and make plays out of it when it's collapsing is very important. My worry is that those are fatal weaknesses that will manifest themselves in him not being able to show off his best attributes simply because in the NFL nobody is working with prestine pockets.
Just because Luck didn't have the arm of Matthew Stafford, doesn't mean he didn't have well above average arm strength.
His arm strength is as good as Tom Brady, as Aaron Rodgers, as Drew Brees and on and on....
Just because you strength isn't elite, doesn't mean it isn't good enough....