Like others have alluded to, if you do want to run an all pass offense you should shoot to have a RS Sr. starter every year and also understand that your backup QB will play a lot of important snaps (read: redzone). I would ideally want my starter to have formation IQ around 90 and the backup to be at least high 70s.
Nitros, curious about your data regarding medium passing. When you say 10% do you mean a drop from 70% to 60% or a drop from 70 to 63%?
I had noticed swings like this before, as well. I generally have attributed lower completion percentages with lower technique at QB, better defenses, the random logic the game has sometimes and QB's playing below 95% effectiveness. I took a quick look around at some teams of coaches that I know are using the offense you mentioned and I don't see a significant difference. There are so many factors to consider (QB ratings, receiver ratings and defense ratings/alignment, pass rush) that it could be noise more than anything. Also, as passing becomes more and more prevalent it's possible there has been a natural adjustment by coaches to prioritize pass defense when it comes to recruiting/roster management. I'm currently experimenting with an all Nickel defense and maintaining an experienced secondary.
Here is one example: https://www.whatifsports.com/gd/TeamProfile/Stats.aspx?tid=54546
The completion percentage is good, which I would expect from QB's with excellent technique ratings. IMO he's leaving points on the field by playing his starting QB at 90% instead of 95% because the backup is more than serviceable and that would be my theory as to why the completion percentage falls in games versus humans. That and the skill position guys are not up to par.
I'm not currently playing at D1A, but my last stint there was 4 seasons ago and I found it still effective despite being generally out-manned talent wise.