So OP got Google to patch a harmless "issue" that could've been used by addon devs to bypass MV3 restrictions. Hope it was worth the $0.
Let's do a thought experiment: if OP hasn't reported it, what do you think would happen then? Even if different ad blockers would find it later and use it, Google would have still removed this. Maybe they'd even remove extensions that have (ab)used it from Chrome Web Store.
Perhaps a hobbyist would code “MV2-capable” MV3 adblocker for the fun of it, forking UBO or something, as a proof-of-concept. How much time would anyone spend on its development and who would install it when the max runway’s a few days, weeks, or months?
So now it's abuse to make the user's browser do what the user wants, for the user's benefit, to protect the user from, you know, actual abuse.
If we think your line of argument to the logical extreme, then being upset at at somebody who ratted out a Jewish hideout to Nazis would shift blame away from Hitler. That's obviously absurd. Both are bad people, and one being bad doesn't make the other less bad. And if one enables the other being more bad then that makes both of them worse, it doesn't magically shift blame from one to the other
Good job.