[popcornmix]

Thanks, that seems to have done the trick!

Is there any reason not to have that setting?

It enables Pi's audio as an alsa device. This shows up in list of audio output devices in kodi in addition to HDMI/Analogue.
While it largely works, it doesn't work as well as the dedicated HDMI/Analogue output devices so we'd prefer it not to be enabled by default (as users will accidentally enable it and may have problems).
There shouldn't be any issue with you (or other users who need the alsa driver to show up for other uses) enabling it - just don't select the alsa device in Kodi audio settings.