This really underscores the point, and it's not just Gruber and random internet commenters opining on EU law while having zero clue about it, it's also Apple fans I respect like John Siracusa and Jason Snell who have a lot of opinions without familiarizing themselves with the facts.
At the very least, they seem to agree that issues with the DMA - and the US DOJ case - stem from the idea that these lawmakers fundamentally misunderstand Apple's approach and why customers choose iOS, macOS, etc.
Tl;dr, the integration is the point and these legal challenges pose the idea that this approach doesn't comport with the law as written and should be disallowed.
1. The EU passed a law that was too complicated for its own good and... 2. Is a law that isn't practically enforceable 3. Lastly, is largely incompatible with how US public companies operate - welcome to Capitalism, it's how the world works...get used to it.
If market forces mean people either choose piracy to get what they want (Napster), that's one thing and regulation can help with that. However, the idea that you can't build a closed ecosystem that operates how you want - before you even get to shareholders in a public company - because this imposes restrictions on citizens, is a weird way to look at the world for a region that is - nominally - still capitalist.