You are generally right, except that you don't seem to know the history of major AWS outages. Failures in AWS in us-east-1, which is the first AWS cloud region, often cause cascading worldwide failures in the whole of AWS - especially failures related to DNS and to DynamoDB, if I remember correctly. That is, AWS workloada running in, say, eu-west-1 (and in fact in the whole of AWS) often start failing or at least having greatly degraded performance/availability because of a failure in AWS infra in their core region.

If AWS themselves can't handle cross region isolation and availability well, my expectations for most companies running on top of AWS are quite modest.