Games

Easy. YouTube doesn't want to deal with actual DMCA more than they have to, so they have their own system that lets big companies do whatever they want, whether the content is legal or not.

Most people don't actually understand how copyright works. And the actual right that's restricted is quite ridiculous but it is how it is...

Copyright is not a right given to the copyright holder, unlike every other right in law. Copyright is a exclusion placed on every other human being on earth from reproducing what you did (except few countries that didn't sign it but practically no one lives there or is a territory that effectively works under another sovereignty which does). This distinction is very important. That is, everytime something is created, every other human now has less freedom since they could do that thing before but no longer can. So if I create an original bunny like character, that is copyrighted to me. But I could always depict that and so could you--had you thought of it. But now you no longer can.

This means that virtually every thing made in relation to that original copyright becomes illegal unless you get permission from the copyright holder. There are exceptions such as transformative, parody, fair use, etc but I'll not get into that for now.

In other words specific to this case, every game footage on earth is illegal. But they only continue to exist by the grace of the companies not telling them to take it down. Some companies actually write into their EULA/terms that fan content, etc may be allowed, but again, those are the exceptions. The rule of law is that everything is illegal to start. And that only the copyright holder and its agents be able to request a punishment for breaking the law.

It's a system where it makes every normal human beings into a law breaking entity first and by doing so, it allows the copyright holder to punish anyone they see fit.

This is not a frivolous DMCA. And even if it was, there has been no case where that was ever punished. Even outright perjury for DMCA--which I've dealt with thousands of times doesn't actually get punished in practise.