Yep, I uploaded a video about the copyright claim. They can't be serious. They claim that the game ambience sounds like their music. Not cool.
Unfortunately a quick search reveals this State51 "company" has a track record of doing this going back years so it seems YouTube hasn't done anything yet to remove them from the platform. They make money by scraping freesounds.org and claiming the sounds as their own to steal ad revenue from content creators. Pretty disgusting and I'm sorry this has affected you.