"What the publishers really want is protectionist capitalism."
You're thinking of large publishers - like EA or Origin. You even used a sly reference to them later on. What is being discussed here is smaller indie developers.
It's like going to your local craft market, buying bulk in discount (and I use that term loosely)...or stealing if they're not looking...a creator's wares, then undercutting the original maker by selling them in your own mall for a fraction of the original purchase price.
"However, outside of accusations, I don't see any provable evidence being supplied. I see a lot of whining from publishers, though."
You only need to do a quick Google search to see that a lot of this happened in the past with G2A.
Having been burned by G2A myself, I wouldn't touch them with a ten foot pole.