Kern is a walk-on that doesn't play. Highly doubt he takes up much coaching resources. That's your comparison for how the Gophers defensive staff would treat Steveson? Well, that's silly.
These are the guys who are going to play ball for us, on the interior DL this year, and try to help us win games:
Pinckney
Carter
Val Martin
MDT
Cheney Jr
(maybe?) Richter
also some very interesting true freshmen (but probably won't have to play much this year) in:
Deven Eastern
Jacob Schuster
That's already a plenty full plate for any DL coach. Oh and don't forget, he has the "regular" D Ends to worry about as well (the Oto guys ... not the "rush end" guys who are really a hybrid of a 3-4 OLB type position and have their own coach in Wegner).
Then in comes Gable Steveson, superstar Olympian. To have any kind of chance of doing anything helpful on the field this year, he's going to need intensive, 1-on-1 coaching for a solid amount of time, just to get his fundamentals (stance, drive out of stance, footwork, hand placement, punch, shedding blocks, start to work on some pass-rush moves) in place. Let alone learning the playbook and where to line-up on a given defensive scheme and for a given look that the offense is showing.
You're really clueless about the reality of the situation, if you don't understand this.