I've found two conclusions:
So my confusion here (as I'm sure it is for many others): where is the line? It seems that apps like Strava and MyFitnessPal allow for subscriptions outside of the IAP ecosystem. These seem to be "readers" to some extent, but you're definitely pushing data into the system.
How have you attacked this problem in your app?
Google Play Store & Apple App Store both have similar policies regarding in app purchases / subscriptions. Apple is much strict about enforcing it.
Example: Songs on Spotify, Content on Netflix, Subscription of Hey.com - they fall under digital category and according to the policy, these apps must provide a way for users to "purchase" these services using in app purchase / subscription.
These companies do not follow the policies. Hey.com is not as popular as Netflix so Apple can suspend their apps.
Google "trying" to enforce policies
Example: Food delivery, Hotel bookings, Taxi, Gym subscriptions, etc.
In this case though, Hey.com is able to get away with it now that there's a limited free version? This part makes things muddy for me.
All cases are described in guidelines and policies.
IAP are not required if you sell goods or services available outside of your app.
Thanks for the note! I got a bit confused by the Hey.com situation and some of the commentary on that. The verbiage on reader apps and all that made it a little unclear.