It works regardless of whether your using desktop or modern UI, if you'd tried it you would know that.
Apparently SOMEONE doesn't understand how connected standby works. When the screen turns black, that *IS* "sleep" mode. In this case, metro apps can still make use of wifi to keep sync'd [mail, weather, facebook, etc] But desktop applications will immediately stop. This is really EXTREMEMLY frustrating when listening to a playlist in Winamp, or when downloading large steam games, as it stops whatever is going on within the desktop program as it goes into it's low power state.
I suggest you give it a shot yourself and see if you can duplicate my results [dare I say, obviously YOU haven't tried it?] If you get different results, PLEASE let me know your settings so I can duplicate them. . because I'd LOVE to be able to keep spotify going all night long with the screen off.