The requirement for making APIs immediately public only applies to connected devices under specific circumstances, which I would expect are a little more solidified at launch on account of how much integration work has to happen between different groups at Apple. AFAICT other APIs can remain private indefinitely unless they are subject to an interoperability request. Assuming the request is valid, Apple has 9-21 months to plan and implement any necessary changes to make the API public, where the time range is based on a self-assessment of the technical complexity of the request.
(See pages 87-88): https://ec.europa.eu/competition/digital_markets_act/cases/2...