At some level in the infrastructure this may be true, but this is not my experience working directly with the RND/Engineering teams and Infrastructure teams on a lot of the big cloud providers. They will undoubtedly have many tricks to get whatever you have on their cloud working again, but there should not be an expectation that they aren't going to just get a fast and dirty fix going. It might work, but it will be a kludge in many cases.
Same with security; quite a few of the S3 on-premises providers have backdoors that allow a person to bypass even the S3 immutable functions -- while I can understand that for specific customers who are using the S3 infra for Storage as a Service needing a way to clean up data from customers who left, such features are not advertised, and IMO, such S3 vendors should not be allowed to call their product "immutable", as it's anything but and most clients wouldn't even know about such backdoors.
The actual tech behind the providers might be pretty nice (this is arguable though...), but I would not say that this has any bearing on their trustworthiness as a provider.