Frost critical of Saban? Now, that is a real stretch and simply nonsense, IMO! I do not read Frost's statement as overt criticism, even a little bit. It was simply a comment about a football game, as much as any football fan who saw the game might have made, and probably did make. When Saban made the change in QB, I told my wife, "Wow, that takes some real guts to put in a freshman at this juncture of the game." Frost gave credit where credit was due. Saban's record speaks for itself and I am not an Alabama fan. I would be willing to bet that if the question was posed to Frost has to who he thought the top coaches in college football were, he would have Saban very near the top of his list.
Yes, I saw this article as a "headline generator," basically. "Let's ask the young upstart coach, who is froggy and full of opinions after his undefeated season, a question about The Grand Master's decision-making." Scott was not by any means critical of putting Tua in at the time - in fact he was pretty complimentary as you point out.
The statement that MIGHT be interpreted as questioning of The Master was "what took you so long to make the guy your quarterback?"
Tua appeared in 7 games at 'bama through the regular season, threw for 8 touchdowns and roughly over 60% completion, ran for 2 td's. ALL of his appearances were in blow-out games in mop-up duty. Tua never saw action in any of the closer games, nor in the loss to Auburn. Here's his stats:
http://www.espn.com/college-football/player/gamelog/_/id/4241479/tua-tagovailoa
Really, it's a legitimate question about how to balance playing time for an accomplished QB - Hurts, who may lack some skills to win games with his arm but is a leader in every way, and the young guy who can light it up, but probably still makes judgement errors occasionally (like taking a couple huge sacks for loss in the NC game) and might benefit from time to observe and develop. Scott knew Tua well, had confidence in what he brings, and given his knowledge and the benefit of hindsight, says he should have been playing more all season. Who knows, he's in recruiting mode, maybe Scott was talking to talented freshmen out there - "come to Nebraska, you'll get a fair opportunity to play right away."
Does anyone think Meyer, Malzahn, Chris Peterson, Jimbo, Harbaugh, Dantoni, or any the other accomplished coaches would have given a "non-political" answer to the question like Scott did? I doubt it. The only one that I can think of that might would be Mike Leach, though he just as likely might have made some oblique reference to obscure the issue even more. Most of the other guys would have just deferred "no one knows those QB's better than Saban, he's spent all year with them, it's a judgment call, etc."