Hi dBC,
Sorry for the confusion, in your scenario it does not affect the monitoring of the direction of power. It is true that in order to read the current direction from the CHSIGN register, only REVRPSEL and REVAPSEL needs to be set to the correct group of channels. The line, "Bit 14 (CHANNEL_SEL) of COMPMODE must be set to the same current channels" is there more as a precaution, since if CHANNEL_SEL is not set to the same group of channels then other measurements by the part will not correspond to the same set of channels as the ones being monitored for current direction. Therefore possibly causing undesired results with other readings such as zero crossing, angle and waveform samples.
Regards,
Dlath