The effect sound of this DJM applied to the channel selected by the effect channel switch at [SEND/RETURN] is not outputted to RETURN AUX channel. Why?

 following effect sounds of this DJM applied to the channel selected by the effect channel switch at [SEND/RETURN] are not outputted to the RETURN AUX channel due to specification.
-SOUND COLOR FX
　DUB ECHO
-BEAT FX
　DELAY、ECHO、SPIRAL、REVERB、TRANS、FLANGER、PITCH