The API already exists, they just don't let other people use it because they're greedy. There's no additional maintenance burden.

Technically cost is not zero.

1. Api designed for internal use could take shortcuts and let’s say use secrets that are and should be internal, or run things as root or something.

2. Proper API maintenance includes at least documentation and some kind of update path/schedule. Internally it’s simpler. (E.g. you must be sure not to leak secret stuff in docs)

But in the end I agree with the notion that these changes for Apple are not a huge burden. (Existing behaviour is anticompetitive)