The conspiracy theorist in me says "yup". Tencent doesn't own a majority of Epic but I am positive this is being done with their (and the PRC's) approval. If Epic wins, they've disrupted the business model and weakened a powerful non-Chinese corporation. If they lose... they still make crazy money and Epic takes the fall. All this is costing is legal fees & some lost profits.
They already lose money from the Epic Games Store, whats a few hundred million more over legal fees.
Perhaps one compromise would be for Apple to put in a purchase dialog that state the benefits of subscribing or paying through Apple: one place to mange subscriptions, one place to store payment data, parental controls - then give the developer a certain amount of space to make their case for going outside Apple. The first time the user does this, they get another dialog to tap through explaining that Apple bears no responsibility for third-party payment systems. Allow developers to adjust pricing to account for the Apple commission. Still require the Apple payment option be available to Apple customers who want it. This would answer the Spotify and Epic concerns. However, to unlock this functionality, the developer fee is increased to offset Apple's costs to run the store. The App Store remains the sole route to getting software on the device and the other rules, like privacy protections, remain. Sony, MS, Nintendo, and Google put similar policies in place.
Never going to happen. Sony, Apple, etc are always going to get revenue off of F2P games on their platform. 3rd party billing skirts the process.