Diana, truth be told, there is technique and artistry involved in both hands. But Bing's main point is certainly to emphasize the right hand. Too many players worry solely about where to put their (left-hand) fingers on the fretboard. But it is the right hand that determines how softly or loudly we play, whether the tone is delicate or forceful, whether we hit all the strings or just one or two, whether we play exactly on the beat or just ahead or behind it, whether we play things straight or "swing" a bit, whether we accent strums, skip strums, mute strums, whether we play a block chord or an arpeggio, etc.
And when we play in a group, if you make a mistake with your left hand it disappears as soon as the next note is played. But if your right-hand rhythm is off, then your mistakes continue throughout and you are likely to stand out.
I would suggest that the main difference between the great dulcimer players and the rest of us is their superior control of the right hand. Most of us can follow the tablature written by those folks, so our left hand goes where it is supposed to, but we don't sound as rich and expressive as they do because we have ignored our right hand as we've learned to play.
Dusty T., Northern California
As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie