Could you help me understand this paper on the "European Muon Collaboration" effect?

[Ignorantsmith12]

TL;DR Summary

So I found this paper https://arxiv.org/pdf/2004.12065 on something called the EMC (European Muon Collaboration) effect which I guess is about how quarks move slower in a proton if the proton is part of a larger atom. Is it, though?

Statistical mechanics might as well be Klingon as far as I can read it, so interpreting an academic physics paper can be tricky. Still, this paper here https://arxiv.org/pdf/2004.12065 struck me as intriguing. I'm pretty sure this paper is about the innards of protons and neutrons, which I find endlessly fascinating, or at least that's how I feel from the little I understand. I have the most difficulty with the contrast between this paper and the "popular version." https://news.mit.edu/2019/quark-speed-proton-neutron-pairs-0220

The popular version just says that the authors of the paper used high-speed electrons for a momentum transfer to determine the "speed" of quarks in a small nucleus versus a larger one, but certain phrases in the original paper jump out at me and suggest something a bit more nuanced is going on. Phrases like "Quark-gluon substructure" and "Necleons are modified" make me think I'm missing something.

Sorry, I'm having trouble articulating what I wish to know, but I guess I'm asking what the phrases mentioned above mean, what this paper is about, and what you think of this work. Does it seem like a well-executed experiment? Do you agree with the conclusions? What do you think?