It's totally reasonable for Apple to use APIs internally that it's not ready to make public -- making an API public is a serious decision with lots of downsides! You've got to support the API forever, and future design directions are constrained.
To expect Apple to make all code it uses internally available publicly is silly.
(If you want some great examples of the extreme amount of work it can be to support legacy APIs, and why it's really important to prevent devs from using private APIs, check out Raymond Chen's blog.)
To expect Apple to make all code it uses internally available publicly is silly.
(If you want some great examples of the extreme amount of work it can be to support legacy APIs, and why it's really important to prevent devs from using private APIs, check out Raymond Chen's blog.)