IANAL but the impression I got wasn't that they are requiring Apple to deliver interoperability, just that Apple can't block it. I.e. they can't create APIs that enable those things and not allow third parties to invoke them.
Even each sub-functionality (for example, AirDrop Contacts Only mode) is enumerated as "shall implement."
So far it seems like a lot of the requirements could be satisfied by Apple just opening their APIs given that an identical solution would in fact be equally effective. The EU could have mandated that the solutions be identical but that would be more restrictive to Apple despite the requirement seeming like it would be less work.
Entertainingly the same reason microsoft didn't lock down the kernel interfaces that lead to crowdstriking everything. MS wanted to be the only security product in the kernel.
Just because something is beneficial to the business (exclusivity) doesn't mean it's not also simultaneously beneficial to users.