Why would Plex care about this? What motivates them to implement this ban?
Honesty, I think Plex is a honeypot and is going to be used to start massive legal suites against people.
A server in a data center will also have a specific IP tied to a specific person (customer of data center or ISP), assuming the server is supposed to be remotely accessible in a reliable way.
This would explain why only some hosters are affected and not others.
Advertising, and operating their own streaming service, presumably involves business partnerships with entities that may not look fondly on self-hosting?
They’re doing it as part of a charm offensive to partner with content creators.