Datacenters, from my understanding are different. They may have hired guards but also have a smaller contingent of actual employees --guarding, doing maintenance, monitoring, upgrading, etc., etc. In addition to rings of security.

The datacentre security is different. They tell you when you sign up for GCP.

Can confirm. Even most Googlers can only go there on pre-approved guided tours, most of the time. And even that isn't common.