If Apple was banning apps from alt stores but keeping them listed in their own store, then it would be a legal issue.
I personally I think it defeats the purpose as well, but I'm more concerned with the right for people to do what they wish with their own device. These antitrust court cases can get pretty specific with what they are addressing.
if you move from ban to, systematically hinder updates, despotic interpretation of store TOS/Guidelines/Rules, APIs their apps can use and others can't which affect competitiveness of the apps, not having to pay their own fees, randomly removing top apps from the app store front/ranking/promotion, TOS which make competing impossible etc.
then they have been doing exactly that for years
i.e. "not ban but market wise not that different"
This was not just subject of the anti-trust case, it's Apple being expected to comply with the EU Digital Markets Act.
(The DMA defined objective criteria to identify a scaled market of digital goods with an uneven playing field for all players. Apple was found to have created such a market and was ordered to rectify this)
The purpose of the DMA is to eliminate gatekeepers' stranglehold over the market and promote competition by forcing them to compete on equal footing. Apple's compliance strategy thus far has been to create an appearance of compliance (alternative app stores, what more do you want??) while fully retaining their chokehold in strategic areas like notarization and core technology fees which completely undermine the goals of the DMA. They remain a gatekeeper who imposes taxes on competition and retains the ability to kill your project (or business) without a due process.
But if they asked to block an app due to breach of a law, they will oblige.
And even if it were true, it is not a counter argument to my assertion that Apple has complete control over what apps exist on every App Store.
No app goes live or stays up on any App Store without Apple’s explicit consent.