Sorry, that is not true. Apple documents all of its platforms quite thoroughly, and Safari is one of them. Theirs is simply not an analogue to MDN.

https://developer.apple.com/library/content/documentation/Ap...

“Apple doesn’t attempt to document general-purpose Web technologies without an eye on its own platforms” might be a more accurate statement, but even that is shaky because they spent a lot of time explaining HTML5 media while killing Flash.