To add another datapoint, we recently faced an issue where Microsoft rolled out a change to their OIDC endpoints, which broke our client's tenant, but not other

To add another datapoint, we recently faced an issue where Microsoft rolled out a change to their OIDC endpoints, which broke our client's tenant, but not other tenants. (It was crashing with an HTTP 500 if the Accept request header was a certain value: the default value in OpenJDK 8). Some days later and after our complaints, Microsoft rolled back the change. I would call this evidence that they do practice gradual deployments of changes. I would guess that this outage was caused by something more complex than MS not slow-rolling their deployment.