I would offer only statistics - as in only a fraction of the time will 100/0 braking be achieved, and an even smaller fraction where it is done safely and correctly. However, 80/20 or even 90/10 can be achieved a lot easier, repeatably, and with confidence. Therefore, training riders in keeping both wheels on the ground using mostly front braking will cause better results and shorter stopping distances as a whole.

This would not benefit those riders who are at the very edge of the bell curve who can brake and handle a lot better than most - just like the motorcycle racers demonstrate when they lift the rear wheel slowing down at speeds over a hundred miles an hour. However, asking your average middle aged Harley rider to practice a stoppie would keep the emergency rooms full all summer. The MSF (Motorcycle Safety Foundation) taught that motorcyclists were widely afraid to use the front brake. Just getting the average rider to go to 60/40 or 70/30 made them incredibly more safe than relying on the rear brake primarily. My Honda goldwing is so large (900 + pounds) that the rear brake can not be activated independently - hit the rear brake and one front brake gets squeezed as well, maximal braking requires both front and rear simultaneously by design. I have yet to see any data or references for bicycle riders, and have no idea how many apply what brake and to what extent, nor how the lighter bicycle/rider system and slower speeds affects things.

I think that the difference between 90/10 and 100/0 might not be all that large anyway, so having either skill would be considered darn good braking.