Yup. I don't know enough people at giant companies to know how many actually do this though. Not just talking having 2 AZs, I'm talking about ability in a DR scenario to fail over, within 5-10 minutes, to a different cloud provider, e.g. AWS → Hetzner, or GCP → Azure.

My gut feeling is that the number of significant applications that have this capability can probably be counted on two hands. Especially since a lot of the largest footprints of software stacks running in the cloud belong to Google and Microsoft, who I'm pretty sure do not replicate their services into someone else's cloud.