You are nit-picky, aren't you? You can enforce some policies with OS X Server and Windows clients and vice versa. But neither platform inherently knows the down-and-dirty of the other. With extra software you can lock down OS X clients on an AD network as if you were running them on a Mac network. Vice-versa probably exists.
It looks like you have to go special-case in order to justify Windows in the first place -- we have special Windows-only apps with no alternatives, etc. And even then you could use Citrix or one of the many alternatives to avoid having to run Windows on the client to use Windows server apps.
If it's "nit-picky" to take exception to someone telling me I can rip out AD and my Windows back end infratructure, and put in OS X servers and my Windows network will work just like it did before, except it will be easier and cheaper and now I can have Mac workstations too.