So "monopoly" as a single entity controlling a single market is a simplistic view of the issue at hand. Anti-trust is far broader than that, where any anticompetitive action can be subject to anti-trust lawsuits/regulatory action.
So the legal argument would be that, because Apple allows for a single messaging app, and interacting with that app requires an iphone, they're effectively preventing messaging app competition.
Apple has a very, very talented legal team though, so, for this to even see argument in court someone's going to have to realllly have to want it, and be able to fund it.
>So the legal argument would be that, because Apple allows for a single messaging app, and interacting with that app requires an iphone, they're effectively preventing messaging app competition.
That is weapons-grade horseshit. You can put WhatsApp, Facebook Messenger and Signal on your iPhone and message to your heart's content. (I know, because I've had the first two on my phone before and they did not get killed in their sleep by Apple's native messaging app).
They don't know what they mean, because there isn't a legal precedent for narrowly defining monopolies to facets of a single company's stores and platforms. It's just wishful thinking phrased authoritatively.
IMHO, the argument is that Apple does not allow any third party messaging app to send message to the built-in messaging application (Apple Messages) on the iPhone. That is Apple ships one messaging app that is the default and may not be removed, and they also do not allow any interoperability with that one messaging application.
Apple Messages is not an SMS application; it's an internet messaging application that falls back to SMS messages when communicating with any non-iOS device. There are some situations where there may be no data network and, maybe, it falls back to sending an SMS message to another iOS device but this is pretty rare.
So the legal argument would be that, because Apple allows for a single messaging app, and interacting with that app requires an iphone, they're effectively preventing messaging app competition.
Apple has a very, very talented legal team though, so, for this to even see argument in court someone's going to have to realllly have to want it, and be able to fund it.