Not sure I can help.. but I have seen this behaviour with my testing with an 8 channel Quicktime clip.
It ‘auto-detects’ the clip as 3 stereo and 2 mono. I can change it to 8 mono or 4 stereo etc, but not manually assign stereo pairs and mono tracks. Also there is no routing for the individual tracks as I see without breaking apart.
Once broken apart I see the ‘unsupported clip’ error message in the channel configuration. This seems to indicate that you can’t configure the channels in an audio clip that is from within a VandA clip.
I can, however, then assign panning to those 8 seperated tracks and then combine them all back in a compound clip – which could all work but seems like a lot of effort at the moment.
I think I can only then adjust the panning by breaking the compound clip apart again… but maybe that’s a good thing.