There are a lot of related issues with how little Unity and it's version of mono provides regarding the process and native window.

This particular bug could be changed to a feature request, but please don't just close it as being by design.

There are some legitimate use cases for knowing your process id and hwnd. My use case is debugging multiplayer by launching multiple instances of the standalone game and changing the window title and positions to differentiate the instances. This is made much more difficult with no process id or native handle. The common fragile work around of getting the handle by window title obviously doesn't work here either.

Thanks for any advancements that can be made here. Any step forward would be a big improvement.