There's a lot more than just recognizing known raw IP addresses used as endpoints.

One method larger services with CDNs use effectively is to use DNS for blocking. When you try to access a site, your DNS request will resolve to a server close to you, with your location determining the domain resolving to a different IP. Then the platform just responds to those requests from outside their normal area with a consistent message. No need to know whether it's actually a VPN or not, the traffic is acting like it is and doesn't really have much of a reason to do that normally.