Well, what we do know, based on data is that we had 2 QBs in a row who were 5* recruits and had been productive earlier in their careers than later in their careers. We also know one of the 2 was at another school prior to coming to Sark.
Now, if you don't want to blame Sark for this decrease in production and accuracy fine. What nobody can deny is that both performed better when the standard script Sark prefers (complex blocking, 5 step drops, long WR routes) is dropped for a simpler one (moving the QB, shorter WR routes, quicker crossing patterns, less complex blocking and designed QB runs). There are multiple examples for both QBs that when allowed to play to their strengths rather than forcing them into Sark's preferred offense both QBs showed demonstrable and statistical improvement in their play.
I'm not sure how you logic around consistently refusing to script a game plan that aligns to the strengths of your players isn't the fault of the person calling the plays. Further, because of the continued issues, opposing defensive coordinators know exactly what sort of defensive scheme to run to be slow or absolutely stop the Texas offense all together. Florida and Kentucky are clear examples. So not only is the QB forced to play an offensive game plan that doesn't align well to their strengths and comforts, they face defensive plans that know exactly how to disrupt that based on the Texas QB, OL and RB skill sets.
Not sure how you logic around not blaming that on the HC and head play caller.