I would to see a breakdown of penalties. Offense Penalties vs Defense Penalties. That would give a better picture.
Or start with offensive holding.
I'd agree with both, any breakdown of what the penalties are would lead us in the direction of something meaningful.
Other than just plain old bias, I've seen two theories floated as to why there is this penalty disparity. One is that teams are better prepared and focused for the Alabama game. I could accept that if it was consistent throughout Alabama's Saban dynasty. The penalties have not been though. The other thing is I've seen it suggested that once the game is decided, once it's a blowout the refs stop blowing the whistle. That kind of makes sense, but it still doesn't explain how Alabama's penalties went up.
So, in lieu of a good explanation, it seems digging deeper into the numbers is the only thing that could bear fruit. I did a little more comparison, now there's two big caveats to this data. #1: There is no Mercer, so that skews the numbers a bit. #2. We really have no idea how many penalties Alabama should be getting called for, we just know they went up over the past four year stretch. So, without that sort of information everything is going to be a bit off.
But, I did figure out the average penalty yards for and against Alabama opponents last season and you can see how this contrasts to how things actually were called against Alabama. These are not the average of Alabama opponents in Alabama games, but throughout their whole season:
2017 opponents opponents (that's a mouthful) penalty yards per game: 46.1
2017 opponents penalty yards per game: 49.2
2017 Alabama penalty yards per game: 43.6
2017 Alabama opponent penalty yards per game: 31.7
What we can see here is that if Alabama was just an average team, they would have expected to have 46.1 penalty yards and they actually had 43.6 penalty yards per game. That's a +2.5 yards in Alabama's favor, but that really isn't saying very much. It demonstrates that a well disciplined Alabama team is still getting flagged about as much as any other opponent.
On the other hand, we have a chasm.
These teams were expected to make 49.2 penalty yards on average against Alabama, and instead they end up with 31.7! That's a massive -17.5 yard gap! It's somewhat inexplicable that somehow Alabama causes other teams to make less penalties, but this gap of 15 yards in terms of what would be expected and what happens does follow the trend where I showed that things were 13.44 yards per game off of where I would expect them to be.