Seems easily distinguished from the case of independent adults who sleep in different homes every night and have separate addresses on all their tax forms, drivers’ license and voting registrations...
They're just forcing 2FA on accounts that meet some kind of threshold of "suspicious" behaviour. There's likely a lot of metrics being used to identify that.
Facebook does prompt people to upload Photo IDs sometimes but I doubt Netflix wants to get that invasive.
(I had interpreted the question as related to how to interpret the T&C. Agree that ultimately, it’s impossible to enforce the existing T&Cs to the exact letter, although some combination of annoyances and mild shamings might affect user behavior and presumably this is what they are testing.)