Hello,
I never really looked at this before, but I think this was done to give us a simple way to hear the effect of the filter. In all the examples, channel A is effectively turned off (filter gain is 0). Once we get an idea of the possible sounds using one filter, we can move foreward to applying settings to both filters. For example, you can try one sample setting for channel A, and another for channel B. I guess the possibilities really are practically endless.
- nate.