The issue is that the burden of validation is so great that the government demanded Google do it themselves, and Google realized the burden is so great that the

The issue is that the burden of validation is so great that the government demanded Google do it themselves, and Google realized the burden is so great that they basically treat all complaints as valid and in good faith, because the effort to actually hand validate each request would make it one of the most labor intensive divisions in all of Alphabet. In terms of liability, Google would rather prematurely remove content (no penalty) than accidentally leave up covered material (violation of safe harbor, could be used by Verizon et al to indicate in another lawsuit that the entire system is flawed, thus safe harbor protection doesn't apply at all, and Google can be directly sued for violation of copyright, something Verizon would love!)