Limited Audio Device Selection in Decklink Capture

Hi, perhaps I'm misunderstanding something, but it appears there is a more limited audio device selection in the decklink mode than in the Audio mode.

I am capturing audio from a Blackmagic Analog to SDI device, from a prosumer VCR which has unbalanced line outputs. Obviously the Blackmagic device has balanced inputs which creates sound that is quite quiet. Boosting the audio input by about 10db in the BM Analog capturing device mostly gets round the issue, but I'm fairly certain the audio quality is not quite up to par.

So I'd like to try one of my other Audio Capture devices such as Focusrite which is seen correctly in the Audio Tab. I thought this would be a simple matter to select it in the decklink tab, but it doesn't seem to be there, even though there is an analog option - not sure what that's for.

Has this been omitted due to audio sync issues or something? Or is there an easy way to capture the sound from something other than embedded SDI audio?

Thanks.