I just checked the usually dependable V281 manual. No real answer there.
FYI, the V281's balance adjustment is unusual--it raises or lowers the level of only the right channel. Weird, but it totally works. On the other hand, you say you get no effect from it, and that's something I can't explain. The +/- adjustment is not huge, but it still should be audible...
Indeed. I feel I don't need this knob, and I never use it. I guess it could come in handy in a pro studio environment however.