That protects against newbies, but we’re talking here about Google employees – modifying and cloning the ICs on the board to fake a verified boot status should be a triviality for people who design their own chips and boards for Google’s own servers, right?
That would be covered by policy controls, not technical ones—it's the same issue as someone taking pictures of the screen with their personal phone. You'd need to address the actual issue that's causing people to do that (ill-thought-out policies, employee actually working for $INTELLIGENCE_AGENCY, employee enjoys espionage,…).
A recent example would have been the data that was stolen from Google and given to Uber – the employees who were qualified enough to design their own LIDAR chips and boards would equally be qualified to circumvent any such protections.
On a Google-approved device, you can still use that device, and copy content to another, non-Google-approved device. Nothing is perfect, but at some point you trust your employees.