Quite aside from this almost certainly being against the T&Cs, I'm not sure what happens when multiple parties claim the copyright. It's literally impossible (I think?) for them all to hold the copyright on the same melody, so how does Google resolve it?
TL;DW - nothing happens, it's an unresolvable deadlock. This "feature" can sometimes be used by deliberately adding many easily claimable works in a video to prevent anybody from monetizing it.
How about having two Youtube accounts and copyright-flagging your own videos?
Then during the 30 day period your other account gets the ad revenue, oh well.