No, it's not. S3 has a very well defined API with easily measureable performance parameters. So AWS updates can make sure they don't make things worse.
This is not possible with a client's workload unless you can actually test it. That's why AWS will warn you multiple times if they need to migrate your EC2 instance onto a different hardware node. Even if it is technically "better".
Of course, the fact that clients trust their workloads to this guy probably means that there was nothing important there.
