There's probably some very good definition of "system quarterback" out there. But for me, I kind of just think of it this way: a system quarterback is a fella who shines in college, but then just goes on to a mediocre (or less) pro career; serviceable, at best, but no longer shiny and bright as he was at university.
It must have been the system.
And that becomes particularly valid if a series of quarterbacks go to the same university, all shine there, and then are all just adequate or worse in the NFL. I mean, think of John Parker Wilson...Greg McElroy...A.J. McCarron...Blake Sims...Jake Coker...and Blake Barnett, all at Bama, all did extremely well in Saban's system, not a single one of them made it in the NFL, I don't think. That's a system that produces "system QBs."
But here's the key point in all that: one can't tell who the "system quarterbacks" are until they go off to the NFL.
And not a single Heupel-led team has put a QB into the NFL yet. I think his two QBs at UCF are both playing college ball this year, albeit for different teams (Oklahoma and Florida State, I think).
In other words, the dude who theorized that Hendon Hooker could be benefitting as a "system quarterback" has absolutely no basis for the thought. It's just something he threw out there.
For myself, I can't imagine Hendon NOT tearing it up in the NFL. He's going to be exciting there, just like he is for us.
Really not worth wasting any more time talking about, honestly.
Go Vols!