[danans]

Yes in the sense that they use all the services and infrastructure that GCP is built in, but no in the sense of using the vanilla GCP interface.

Instead many aspects of GCP's management console are handled by different internal tools, often command line driven. IME they are often far more unwieldy than GCP.

Sometimes this makes sense (far tighter access controls and configuration change controls than a typical company), and some times it's just because of legacy ways of doing things.

I worked on a team at Google that used the internal GCP to serve some code/content for a specific feature, and it was in some ways it was more frustrating than using just either the normal internal systems or just vanilla GCP.