I think an apology before they've had a chance to review everything that occurred would be rather empty, don't you? "I'm sorry you're upset"?
I far prefer what they've stated they're going to do which is stop the activity they know about immediately, and to review how we got to this point.
If, on the off chance, the professor was being honest about ensuring they weren't wasting anyone's time, and ensuring no bad code made it into the kernel, then the situation becomes a bit more murky. They'd need to go through all of the associated emails both public and internal to validate that.
If on the other hand this is in fact a duck, I would expect them to both to issue a meaningful apology at that point, as well as lay out the steps they've taken to ensure it doesn't happen again (which they've indicated is their plan). And hopefully restore the trust of the OSS community.
It is more likely that you just have an administrator that became aware of the issue, they won't make an apology until they understand what happened.
The job of UMN is to get the facts first, and then determine actions. If the OSS community (and others) feel like the actions don't match the facts (or if they feel the facts don't match what actually happened) they can apply their own set of actions.
When the issue has gotten actual attention an apology to the kernel mailing list might be appropriate, but as someone who has been apologized to many times it all just becomes meaningless, who cares if you say you’re sorry. I care what you’ll do about it.
The best apologies are the ones that are done after some reflection, not under duress, and not purely for reputation.
The way their statement stands they can investigate themselves and determine they did nothing wrong, we'll have to see what they say down the road.