I disagree with you argument — _we_ don’t know what the copyrighted portion was, but that doesn’t mean no such portion exists. Likewise, asking-kids-under-20 is not a method I’d generally endorse for legal issues.
Per the article, it is unclear what was copyrighted. It’s possible that YouTube knows but is not making it public, or maybe even YouTube doesn’t know. I definitely feel that YouTube’s handling of copyright issues is annoying, I feel like the creator should be told what YouTube knows. But that’s not an issue with copyright itself.
Yes, but copyright has fair use exception. And in theory when you send a DMCA, you are suppose to consider fair use[0], so this seems more like abuse.
[0] https://www.arl.org/blog/9th-circuit-holds-fair-use-must-be-...
Youtube doesn’t know, because the DMCA doesn’t require the complainant to be very specific. The right course of action is to deny the complaint and make a counter complaint to youtube. This forces Youtube to reinstate the video, and forces the original complainant to take their complaint to an actual court. A copyright bully will simply never do that. They’re relying on people to give up at the first step, without making a counter complaint.