[Audio][Niagara] - Audio Spectrum only reacts to Channel 0, despite setting to another channel

While doing some extra testing of the Submix Analyser fixes, I noticed there is a setting to set the channel of the submix to give the analyser. It always works for channel 0, but changing it to anything else doesn't appear to react. Also occurs with Sample Audio Buffer.

[Link Removed]

1) Launch AudioQA
2) Import the attached stereo .wav file, which plays audio in the right channel only
3) Drag the Sound Wave into the Default level as an Ambient Actor
4) In the Content Browser, go to Assets > Niagara and drag NS_SoundVisualizer into the level
5) Open NS_SoundVisualizer and open the patch on the Sound module (under Particle update)
6) On the Audio Spectrum, set the ChannelIndex to 1 (0 is Left, 1 is Right)
7) PIE

Expected Result:
The Niagara effect reacts to the audio in channel 1

Actual Result:
The spectrum analyser doesn't react