OK - maybe this needs reporting as a bug then ?
But - I've just tried a very quick test: I started with the windows 8 game template that comes with construct 2, added two sound files from the free bundle (an .ogg and a .wav) and exported to windows 8 (and also to windows 8 phone) both exported folders contain media sub-folders and in each media folder is only the .wav files (no ogg).
So maybe a little more research into sound formats is required ?
edit - I obviously type very slowly ! (but in my defence I was checking things as I went along)