Article 3.1.3(b) says:
"Apps that operate across multiple platforms may allow users to access content, subscriptions, or features they have acquired in your app on other platforms or your web site, including consumable items in multi-platform games, provided those items are also available as in-app purchases within the app."
This is in contrast with 3.1.1 that says:
"If you want to unlock features or functionality within your app, (by way of example: subscriptions, in-game currencies, game levels, access to premium content, or unlocking a full version), you must use in-app purchase. Apps may not use their own mechanisms to unlock content or functionality, such as license keys, augmented reality markers, QR codes, cryptocurrencies and cryptocurrency wallets, etc."
Now... to simplify the text, let's remove some parts:
3.1.3(b): Apps that operate across multiple platforms may allow users to access [...] features they have acquired in [...] your web site
Now notice what 3.1.1 says:
Apps may not use their own mechanisms to unlock content or functionality, such as license keys, augmented reality markers, QR codes, cryptocurrencies and cryptocurrency wallets, etc.
In case you don't know what "etc." means, it's latin for "et cetera" which means "everything else related to a list of nouns".
In other words, 3.1.3(b) says that you may allow user to access content or features acquired outside the App, but 3.1.1 says that you can't use any known mechanism to access that content.
Am I mad? My multiplatform app should allow users to unlock extra functionalities by logging into their existing account, but it got rejected 11 times.
I'm at a loss... there's no chance the review people would understand, they're just dumb. And I also had a phone call which did not sort any effect.