Courts in EU and US have all agreed that Apple is well within its rights to charge a license fee for use of their technologies. No different to companies like Epic or OpenAI.
And I would have doubts that any regulator would want to get into the business of deciding what is a fair percentage to charge for an SDk or API.
And I would have doubts that any regulator would want to get into the business of deciding what is a fair percentage to charge for an SDk or API.