Not sure about the G3 as I haven't shot any videos with it, but on the G2, "Audio Zoom" is touted as a feature. That is, if shooting a video of stage of a school concert, the sound focus reflects the wide video view. If you zoom in on little Johnny, the audio focuses with the video zoom, focusing in and around Johnny (using the 3 microphones on the device). Possibly this feature muffles out the overall sound say, if the sound system speakers are to the sides of the stage.
I completely understand the problem here; that is, likely what is desired for a school concert in my example, is constant sound volume and quality with video panning and zooming throughout the video. My guess is that LG's Audio Focus feature was meant to bring little Johnny's singing to the forefront by focusing in on him when the video is focused in on him.
Just my musings, not based on facts -- except that Audio Focus does exist as a LG G2 feature.