> A common pattern in Apple platforms has been for APIs to be private initially, then made public 2-4 major versions after introduction, once the bulk of the design churn is over with and it can remain relatively stable.

I think DMA is what it is partly because Apple has stopped doing that for signifiant chunks of functionality, and started removing features available to third-party developers. See "Apple restricts Pebble from being awesome with iPhones" https://ericmigi.com/blog/apple-restricts-pebble-from-being-...