Would that be the same thing that Seamus Ennis called a “shiver”? You flex your hand at the wrist and let the finger for the desired note vibrate over the tone hole, is the best way I can describe that.
I learned how to do it while attempting to do trills. I also thought the “bounce” name was confusing, but then I noticed that if I only “trilled” once it was a bounce.
The name is as it suggests…you bounce your finger upon playing the note; not quite the same as playing a trill where your focus is on lifting the finger. Bouncing seems to just happen when you focus on bouncing the finger down as if it is a rubber ball. Obviously it involves lifting the finger, but for some reason if you think of it as a lift, it won’t work, at least not for me. It’s more of a slam down and let the finger lift and slam down again. In this sense it only works when stepping down the scale (A to G for example) rather than going up.