Netflix absolutely enforced this in the US last year. I was sharing an account with my sister and we started getting notices about choosing a "home base" for our devices so Netflix could register it on their side to enforce if anyone outside of that initial IP began leveraging it.
My family got several of those notices. One time me and my sister were not able to watch anything using my mother's account. We stopped using Netflix altogether but a few weeks later my wife opened the app and we were able to use it without any issues. I still see the option to pay for "sharing" or whatever it's called but we don't have it enabled