Apple's 'moral assumption' is that Spotify would like to 'freeload' off of their store. The App Store is provided with the intent that services which are based off of it contribute back to the App Store.
Open-source software is not provided with the 'moral assumption' that users contribute back.
There is no hypocrisy here. Apple is criticizing Spotify for trying to sidestep the moral expectations of the App Store, but Apple itself is not sidestepping moral expectations of the open-source products it uses.
> Windows and GNU/Linux are doing fine.
Are they? In what context? Do you really think Windows does "fine" for the average user, and that they are not at a huge risk of malware, terrible software, and more?
It's also disingenuous to say that security problems are not in large part caused by how open available distribution channels are. We have proof showing that the App Store has provided an objectively more secure environment for the average user than Windows or even the repository model.
No, the App Store is provided to drive iPhone sales. If you couldn't install third-party apps on iPhones, no one would buy one nowadays. The market has changed drastically since the iPhone's launch, when a public SDK was still unavailable.
> We have proof showing that the App Store has provided an objectively more secure environment for the average user than Windows or even the repository model.
I'm not convinced that's true. Apple has also invested heavily into app/process isolation on iOS itself, and a permissions model that keeps apps away from sensitive data without the user's consent.
Not to mention the fact that it's more the review process that keeps malicious apps off the phone. Google Play Store is also an app store, but they don't review apps anywhere nearly as closely.
Either way, an app store is not a prerequisite for a review process.