it doesn't, even if you just want stereo as two mono files.
I use the AudioMove software for multi-mono. So you'd take your 6-channel render and drop it in this app to get you 6 mono wav files.
get it here -
https://public.msli.com/lcs/audiomove/
Demo video I made -
http://reaperblog.net/2016/03/quick-...audiomove-app/
Drag and drop, can't be easier.