Earlier quoted context omitted.
We have an old "quiet part out loud" corporate story. It's about how one arm of Google using our service and wondering why it had so much downtime, only for us to point at their GAE arm and say "when they're down, we're down". They went and talked to GAE and - funny enough - were able to correlate the downtime they observed with GAE downtime. GAE uptime improved, for a little while. Yeah, we're on AWS now too.
Does Google run on GCP?
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.