After a better look it seems like this is not actually required for things to work properly, and what I thought was a dependency on rpcss was apparently an unfortunate and rare race condition during services shutdown (winedevice.exe getting stuck calling QueryServiceStatusEx), which has been resolved by terminating the services.
I still believe this is somehow a valid change though the title is incorrect:
According to MSDN, "\pipe\xxx" endpoints are only supposed to be used with ncacn_np whereas ncalrpc is supposed so be used with arbitrary "port" which must not contain any .
The ncalrpc transport actually builds an internal \.\pipe\lrpc\xxx pipe name from the arbitrary port name, and this ends up being \.\pipe\lrpc\pipe\wine_plugplay for the plugplay service. It works, but maybe it's not even supposed to.
I'll update the commit message and resend the series, reordered.