IANAL... I wonder if random AMZ customers could use this clause in a case without AMZ's cooperation?

It looks like the intent is to protect AMZN's customers from IP lawsuits related to their use of the service offerings.

So if you were sued for using VMs or S3 storage by a third-party who had used AWS, you could invoke that clause.

That's the intent, but is the language specific enough to limit its application to that?