Having a Netflix subscription is independent of any app? I assume there's a requirement to confirm any download on Xbox, but don't know for sure.
Sounds like it's a feature of the app "store" (what's it called on Xbox?), so make you confirm your downloads (which could be purchases if it were a paid app) before downloading.
Similar things exist on iPhones, PlayStore etc. You can disable them on some platforms, but not all. I'm not familiar with Xbox to know whether it can be disabled or not.