What I don't understand is what the theoretical endgame would have been here?

Putting the circumstance aside that their submissions are effectively indistinguishable from malicious content (and should be treated as such anyway), if you stay in their line of "it's just research", then getting banned is just another possible outcome that should have been expected as a possibility from the beginning, no?

What they are doing now is basically saying "Yeah we know we did this to see whether actors like us get blocked, but you see, it's US, we should clearly get different treatment".

The thing that really confuses me is they keep pointing out that the research was done in fall of 2020.

Like that matters.

Like they got away with it and the statute of limitations should be up and they shouldn’t be punished at this point.

The ban happened now because GKH got fed up with a different researcher from the same group who was submitting (qualitatively) bad patches and said that it looked like a continuation of the "Hypocrite Commits" work, which the kernel team strongly objects to.

Thus it's a relevant clarification that only small set of patches in 2020 belonged to that project, they did not continue it, and the recent patches are not related to it and are merely bad, not malicious. (Of course the student should have done a better job with that, but it's a categorical difference between him also trying to trick people vs merely messing up and getting in extra trouble because his advisor pissed off the kernel team earlier)