Pretty much nobody at Google has that kind of access. You can be an SRE of just about anything at Google and never access user data. The "break-glass" means of emergency access is ridiculously booby-trapped. A person wanting to do this thing has to 1) badge into a special room, at which time both production security and privacy incident teams are notified, 2) use a special hardware security device that is used for no other purpose than to activate a VPN box with a hard-line into the production network. By the way if a random Googler just rolls up to a datacenter without a reason to be there, that also triggers privacy incident response, even though physical access to production storage is virtually useless due to all the encryption.

I would say it is much more likely that Google will accidentally lose the organizational ability to become root-in-prod, than it is that a person has done this thing without being noticed.

In short, insider risk cannot be mitigated with hiring practices. You need robust technical measures against insider risk.