It was created by a handful of teams comprised of smart people over a few console generations and 14-15 years of code layered on old code...
The "unintended consequences of code" is VERY much in effect here...
I'm rooting for you!
If you definitively figure any of this stuff out beyond conjecture and anecdotal evidence, you'll be among (if not) the first to do so...
I do tip my cap to you on the Heisman "Speed Cheat" for the CPU tho...this is my first foray into that level and I'm not impressed for exactly the reasons you described AND the fact that in dynasty games, I've seen four drives (two by me / two by CPU) that ended up in a "first and goal" situation that was prompted each time by VERY suspect series of events that then (each time) culminated in FOUR goal line stands...
Heisman (for at least the time being) seems about as "roulette" triggering as HFA...
Well, IMHO of course!!!