Sluggo,
You are spot on here in your observation. Watch Hack's footwork, his hands through transfer and his quick sets in the pocket. Those all indicate that what you're saying is, in fact, the case.
Case-by-case, you could conclude the following from 2013 to present:
Footwork - In 2013, play drops were executed beginning with the pivot and drive through transfer. This is coached using the QB clock (5-6-7) and utilizes straight, counter and boot action through the give. In 2015, you see zone-read pop pivots with quick sets and slide drops. All vertical and all short.
Hands - In 2013, Hack was a one-handed QB in the mold of Tom Brady because that's how you operate in pivot to straight, counter and boot actions. In 2015, Hack is a two-handed QB because that's how you operate in pop pivot zone schemes.
Sets - Hack is no longer operating as a drive and gather QB who stretches his drops and sets up in a variety of locations depending upon action and route. He always sets up through read to quick or slide sets in the interior of the pocket.
The last point I would make is one that was raised in the other thread. That is the presence of tag plays. O'Brien's offense did not have tag plays as such. Tags, as you are aware but for the benefit of others, are a zone-quick concept where you call a running play with a frontside pass tag tacked on the end. Teams that I'm familiar with will most typically do this with the bender series and the double series tagged to quick read and pin certain elements of the defense through indecision.
Based on all of this, I wholeheartedly agree with what you are saying and see some of the same square peg, round hole stuff that you do. Bottom line, they have to be flexible enough to adapt scheme and meet in the middle.
Take care.
ziplock