** Nuanced point alert **
Looking at these numbers without any context can be misleading. To explain:
To my knowledge the QBs weren't put through a drill where they were instructed to throw as hard as they can. Rather, each made choices about how they wanted to pass to make the completions.
Take Jackson for example. I heard Mayock specifically say that Jackson wasn't really ripping it, he was playing it cautiously and aiming the ball to ensure completions. If you accept Mayock's observation, you have to interpret Jackson's 49 as an aimed throw 49, not as his top speed nor necessarily reflective of his arm strength.