Why do my multiple external audio sources get bounced to a single mono channel?

I'm working on a project using a Canon DSLR and two cavalier microphones. I've imported the media and synchronised the video (with embedded audio) and the two external audio recordings. No problems there.

The issue I run in to, is that the two lav. mic. channels seem to be being treated as one mono audio component. This means that I can't selectively edit between the two channels when in the timeline, since I can't expand the audio into its two sources

Here's a screenshot of when I take the synchronised clip and right-click 'Open in Timeline':

You can see the separate connected audio tracks.

When I select the synchronised clip, here's what I see in the inspector:

Not that the embedded audio from the video shows up as stereo (which would allow me to change it to dual mono and have full flexibility), however the connected audio only shows up as a single mono track

Any help would be greatly appreciated!

Ben