I wasn't talking about what 'the tools do, under the hood' (dammit, typical windows speak), my point was that your operating system is a black box. dammit there isn't even source code available.
Darwin source code no longer exists? This link no longer works? In an education environment you can also get access to the NT source code. Either way, it's all irrelevant to most programmers even those on Linux.
IOW, windows experts know how to use windows, unix experts know how unix work (and therefore, due to the openness and clarity, a lot more about how their computers work).
So OS X is no longer Unix? No longer bundles all the Unix utilities? No longer uses POSIX?