I shuddered a bit when i heard that some GCP services are just external wrappers over internal systems. Feels like a bad setup for everyone involved: customers, wrapper owners and internal system owners.
Was mentioned in an onsite interview i had with them a few years back. Maybe i misunderstood but it seemed that internal teams didn't integrate with the same API as external customers. Not sure the other reply means that the "wrapper" doesn't exist or the wrapper's are just named the same as the underlying service or i just misunderstood the point.
My impression (I work at Google) is that internal interfaces to some of these services have a lot of Google-specific stuff that are hard to map to non-Google requirements.