It must be nice being as large as Netflix and able to pull a move like this without Apple threatening to remove you from the App Store due to non-compliance. Apple wouldn't dare remove the Netflix app but a smaller developer wouldn't have a chance in hell of getting their app through without being forced to use IAP.
There are plenty of smaller apps that do the same thing. One that comes to mind is ACloudGuru.
Well it's anecdotal but when we have tried something similar (Buy on our website and use the app as a 'dumb client') on a couple of different apps they refused to accept it.
The official App Store rule is that you can’t have a link from your app to your website that would allow them to purchase digital goods that can be used within your app and you can’t mention how to subscribe outside of the app.
Yes, i'm well aware of this. Perhaps you don't have much experience dealing with the app review team but in our experience these rules are more often loose guidelines. At the end of the day it comes down to the reviewer you have and how you can benefit Apple.