Of course Apple is going to build features their customers want and those feature are going to line up to some degree with what is available on the app store. This, in itself, is not a problem as any IP theft here should be covered under IP laws.
The real issue is that when Apple does release an app (especially a paid app like Apple Music), that they don't compete fairly. This happens in three ways which are mentioned in the article:
API parity:
>> the in-house version often benefits from functionality that outside developers are prohibited from using. Apple Music, for instance, is the only streaming service that is entitled to take full advantage of Siri. Apple says it plans to change that policy in its new operating system, iOS 13. Apple’s walkie-talkie app, which launched after independent apps had proved the appeal of the concept, is the only one that can operate on Apple Watch.
Information Parity:
>> what makes Apple’s practice different is its access to a trove of data that nobody else has. The App Store, where the original apps were offered and competed for downloads, collects a vast amount of information on which kinds of apps are successful—even monitoring how much time users spend in them. That data is shared widely among leaders at the tech giant and could be used to make strategic decisions on product development
Power imbalance and IP lawsuits:
>> They generally don’t sue Apple because of the difficulty and expense in fighting the tech giant—and the consequences they might face from being dependent on the platform.
You said:
> Whether copied or not, I'm extremely skeptical that App Store analytics are influencing OS features. It's never been Apple's style to be analytics-driven.
Do you have a basis for this? This seems to be contradicted by this quote:
>> That data is shared widely among leaders at the tech giant and could be used to make strategic decisions on product development, said Phillip Shoemaker, who served as Apple’s director of App Store review from 2009 to 2016. “I think Apple gets a lot of inspiration from apps that are on the App Store,” he said.