Uh... the repo has literally been taken down by GitHub: https://github.com/rockchip-linux/mpp

Not sure what you're trying to say here. DMCA takedown enforcement is 100% the responsibility of the Online Service Providers per statute. It's the mechanism by which they receive safe harbor from liability for hosting infringing content.

Yes, but Microsoft/Github do not make any determination about the validity of the claim.

Once a valid (from a process perspective) claim is submitted, the provider is required to take the claimed content down for 10 days. From there the counter claim and court processes can go back and forth.

I think you may be astonished to realize a (the?) majority of DMCA takedowns are neither checked nor legitimate...

You can post your thoughts, feelings, and opinions on google blog, and I can submit a DMCA and google is required to take down your thoughts feelings and opinions immediately without verification.

Wrong. A DMCA notice is not a court order and Microsoft/Github are not legally required to follow it. They do take on liability for the purported violation if they do so but if it's a nonsense allegation that doesn't matter.