Google Custom Search was down for a similar time period. (Outage lasted longer than GCE, but seems likely related.)
No they don't use gcloud to host their own apps. Yes that's ridiculous.
Which is exactly why I won't use GCE. If Google isn't confident enough to use it for themselves, neither will I.
The fact that Amazon dogfoods AWS is a major advantage for them.
Even if Amazon.com uses AWS (the extent of which seems it may be a mixture of marketing hype and urban legend), there are many ways AWS could fail that affects customers but leaves Amazon.com unaffected.
It would be hilarious if they use to host their services on AWS or Azure.