At least the Windows one is the function I wasn't willing to assert exists. However, it does not appear to have the "a lot of other stuff in that snapshot which is not [linearizable].". The resulting structs[1] are missing many things that ps may want to display in Linux, which you will have to fetch nonatomically.
The OSX one, I don't know; I scanned over the docs and it went over my threshold for what I'm willing to poke through for a HN post.
In other words, this is exactly what I left myself an out for, and I see nothing that contradicts what I said for the Windows case.
[1]: https://msdn.microsoft.com/en-us/library/windows/desktop/ms6...