No I get that I should say his development as a useful backup/spot starter/2nd QB.
I think people could read what I said as overall development or just ability to read defenses, have appropriate footwork, etc...
Take the pass to CJ in the end zone. That's a pass where his arm talent won't allow him to make that throw probably 1/2 the time he attempts it. Working on his footwork, not drifting back, etc will allow him to consistently hit a throw like that.
A QB with a stronger arm wouldn't have to worry so much about having his feet set or even drifting which will take time and reps to improve upon and may be able to hit that throw 2/3 of the time or maybe even more. So superior physical gifts could allow them to develop faster as a useful spot starter/backup cause it's easier to cover up those growing pains while learning other aspects of football. The QB will just probably have a shorter timeline to providing gameday value or as I meant to put it develop into a gameday useful player.
A QB with other physical gifts just helps even more when you consider rushing, escapability, height etc... It makes the mistakes that come with development loom less large and their ability to produce come that much faster.