Sure, the YouTube (not Chrome Web Store which is a completely different organization) system requires far more of creators and far less of "owners" than DMCA specifies with respect to copyright. We're still talking about copyright. The extension under discussion cannot be construed as violating copyright, or even facilitating violation of copyright. That's why even the crazy overblown threat letter doesn't mention copyright. It probably would have, even if it did so without justification, if the end goal had been to take down a YouTube video. The end goal in this case was actually to take down a Chrome extension, which is only similar in the sense that the people who make such a decision also work for Alphabet.