Does it come down to The Law of Leaky Abstractions?
>> https://www.joelonsoftware.com/2002/11/11/the-law-of-leaky-a...
Which means that if Apple wants to change something eventually, then they will possibly break downstream abstractions and then people will complain and the downstream abstraction will say "Well Apple changed their API, it is their fault". Letting someone do it from square one would be enabling that future scenario, as it isn't "if" it changes, it is "when".
If it was an open source API that would be different, but Apple's is closed source, that is Apple's philosophy at the core. It is a closed API yah? Not even an open spec right?