In Apple’s case it mostly means that the API:s Apple use for the AirPods use should be available for others to also use. Apple is not allowed to deny or punish headphones from other manufacturers that want to use those API:s.

This is not quite the problem.

There are multiple issues at play.

The two main issues are:

1 - Sometimes processing is done in private cloud servers for complex translations. Apple is not allowed to do that for EU users. Full Stop. Even if it were not prohibited by EU law, you still have issue 2.

2 - It's unclear whether or not Apple can charge. If another dev uses the APIs, and it triggers a call to the cloud, who pays for the inference? Until Apple gains clarity on that, charging could be considered "punish"-ing a dev for using their APIs.

My own opinion? Issue 2 they will get worked out, but it won't matter because I don't think the EU will move at all on issue 1. I think they see data privacy as serving a twofold purpose. One, protecting their citizens from US surveillance. ie-National Security. And two, part of their long term strategy to decrease the influence of US tech firms in the EU. Both of which I think European policymakers and European common people feel are critical to Europe.

On-device API use is what is relevant here, services such as servers and interference services are out of scope. The DMA clearly allows companies to charge for service use, but they cannot deny API use for any competition who wants for example to use the quick pairing feature or low-latency communication.

They can design the API in such a way that you can provide your own interference solution, or just disable the cloud interference. This is purely a business decision.