This goes way, way back. Here is an article where Saban says they were in the 3-4 less than 20% of the time,
back in the 2011 season...
Nick Saban explains the origin of the terms. Who will fill these important roles this season?
www.al.com
that 20% has continued to shrink every year as more and more teams run more 11, or even 10 personnel groupings as their base offense. One of Pruitts seasons the only time we ran something that looked remotely like the 3-4 was on goalline/short yardage. Our use of that grouping has legit been down in the low single digits for a long time.
Go look at the defensive stats - you'll usually see the 'star' pretty high up in tackles.
To your point though, there have been years where we played the nickel with a grouping that was 2dl, and 2olbs more, and years where we played with 3dl and a single OLB more, and some years that it was a pretty even split. It still operated like a 4 man front, we just had guys better/deeper skills in different placed in the depth chart. Gol*ing ran a lot, probably more than he should have, with 2DL and 2OLBs. I kinda got it, as our best players through his tenure were often the OLBs. Pruitt leaned more into the 3DL 1OLB grouping except for situations that were a bit more pass likely.