As far as I can tell this basically means that all apps must be approved by Apple to follow their “platform policies for security and privacy” even if publishing on a third party app store. They will also disable updating apps from third party app stores if you stay outside the EU for too long (even if you are a citizen of an EU country, with an Apple account set to the EU region).
The idea that preventing app updates is in line with their claims of protecting security is utterly absurd. “Never attibute to malice what can be explained with stupidity,” but Apple isn’t stupid.
It gets a bit more complicated than that when it comes to antitrust law.
Apple has less than 30% mobile maket share in the EU, antitrust laws usually kick in above 66%, and very rarely above 50%.
There are other laws being worked on to combat shrinkflation, and others to curb all the tricks of removing features after the sale, but they’re not here yet, and it remains to be seen whether they’d apply.
I don’t think that’s how to look at it. There’s clearly something less than optimal about having these huge gatekeepers (as I believe is the term used) and the EU is trying to limit their power.