As one gets older, we do not necessarily get wiser . . .
Have survived several other harmonic vibration events on other bikes and was always able to control the vibration by coasting and clamping knees to toptube and sitting upright and NOT applying the brakes.
In this case it did not have any effect and bike was slaloming in and out of the oncoming lane on a curvy/fast/smooth mountain road.
Did not want to be a hood ortnament on a truck coming around the bend, so tapped front brake and did my paratrooper roll over the bars.
As I was doing my roll, looked under my right arm and saw another bicyclist right behind me. He rode over the top of me and cracked his helmet.
Fast crashes are survivable.