Maybe they weren't using SRWLock, at least last time I checked std::mutex didn't use it with MS STL(They were stuck with critical section because of binary compatibility).
(And I wouldn't characterize myself as being overly impressed... for my particular scenario I wrote, "if you have a poorly written app that's bottlenecked on a lock, then consider targeting Windows to make the best of a bad situation." A better approach, of course, would be to just improve your code!)