As of now, you can link channels together as stereo channels and tie several features together so you don't have to manage two channels separately while they do the exact same things (fader level, name, gain, etc.). This makes it simple to set up your user layer and reduce the visible channel count since duplicates need not be included (show only L channel since R follows the fader and other changes). That's efficient.
But when recording to SD, you have to select both channels independently. We had to record to SD in church yesterday because our typical recording process is bound to the media computer, and it took a dump. Our sound guy recorded by selecting from the user layer, but that means two of our stereo sources missed out on half the signal in both cases because he selected the visible channels (both L) and the other half of the signal (R channels) were hidden (again, which is efficient for mixing and that's one streamlining benefit to the user layer).
If linked channels could be set to arm together (or just did by default), that would prevent such oversights and would cause only the added complication of recording space per card. But given the far more monumental problem of missing half your signal on (particularly in our case) a potentially-critical input, that's a small price to pay. Add in the option to turn off that link, and the problem is eliminated.
