Thanks for clarifying your position, but I still don't quite see how this applies to Parler in terms of their decision to host upon AWS. There are many thousands of other hosting companies worldwide, they didn't have to use one of the big three IaaS providers.
It seems more like poor planning on their part: over-reliance on specific services of a single provider, and no disaster recovery plan for if this is made unavailable. Particularly considering the business they're in - publishing controversial content that gets its users banned on more mainstream social media sites. They would have been wise to have a backup plan for hosting.
On the other hand, if you were also passing reference to the app store duopoly (as the report mentions this), I agree with you on that. At least on Android a banned app can be fairly easily side-loaded; iOS users are entirely subject to Apple's whims on what their device is permitted to run.