This young man has all the physical tools, what Casserly I believe was trying to say is Kyler doesn't have it between the ears and that was a stigma Kyler's father also had who was a 2 way guy in baseball and football. Kyler has the arm, speed and athleticism, but you have to be able to think on your feet and on the fly as well as know the playbook and some NFL teams value that the 'old school way' and many teams don't care.
You can't compare Kyler Murray to his predecessor neither as both are totally different physical specimens. Michael Vick wasn't a cerebral QB and got by on pure athleticism and arm strength as well as his legs. In today's age of a big field that is getting smaller with larger linemen who are faster, bigger and stronger, QBs have to be able to read a "D", run through the "D" and find the open WRs/TEs while on the run or eluding the pocket.
I wasn't a big fan of Mayfields but he had his moments in his rookie year and he made some adjustments, however, in 2019, NFL teams will have enough game film on him to make adjustment as well. Small QBs in the NFL have not been totally successful, but a handful along the way did purdy good like Tarkenton, Brees, Flutie, Wilson, and two have Superbowl rings in Brees and Wilson.
I believe some of the hype from Charlie's words of what he "heard" from other execs he may know, which probably are consultants since most GMs are younger these days, was to sway teams to make trade demands to move up in the draft or devalue the ability of Kyler Murray between the ears.
Kyler can do all the physical things but I don't think he's as good as DeShaun Watson was coming out of Clemson.