Apple is highly compartmentalized.

I had a friend working on iPod frameworks and he was free to talk with me about new iPod developments because he only learned about them the same was I would: by watching the public announcements on YouTube.

A bunch of old Cygnus colleagues work at Apple. One of them, working on the debugger, said he was shocked when macOS-on-intel came out because he hadn't heard about it. That team had had to make their own fork of the toolchain (and presumably the OS!) to fix their own bugs, until it was publicly released. He said he thought a few weird bug reports about things like stack frame assumptions that came in from random external addresses (about the generic gdb) were probably, in retrospect, from the Marklar team, but that he would never know.

I'm convinced one of the strengths of the Valley is the de facto permeability of NDAs, and I actually consider Apple's level of secrecy a weakness. Though they seem pretty satisfied with their approach :-).