That is correct, sorry for the typo.
The Sub group will send to the L / R automatically, so you don't need to send the channels going into the sub group to the L / R mix ( the switches on each channel strip ). The FX however cannot be sent back to itself or nasty sounds will ensue. So the FX return channel can be sent directly to the L / R/ mix.
With a need for only 4 monitor mixes though, you will have 2 more auxillary mixes to use for FX! So you don't need to worry about sub groups anyway. The 5-6 aux mix can be set for pre or post and you want to set them for post. The return can be any set of channels you desire, but the stereo channels are always a good choice.
Have fun and do please post results and impressions!