I did a little judo when I was young (only 3 years IIRC, from 6 to 9) and it saved my life many many times, falling from horses, bikes, motorbikes, anything really, at reasonable speeds and with almost no protection.

When falling from something that's moving, you will continue to move when you hit the ground; to limit hurting yourself you need to roll and not skid. The way to do that is to put yourself into a ball, and to do it by instinct (as of course you don't have time to think about it).

It would prevent you from falling with locked wrists and breaking your arms.

You'd still get scraped up and hurt, of course, but falling at 20 mph and not running into a brick wall doesn't have to result in broken bones.

Actually, it does a whole lot. If you have a jacket on, you will avoid getting scraped. And I've fell actually going 20-30 multiple times on the boosted board, as long as you don't fall stiff armed, and have some torque to "roll off" you will be fine. I'm only about 150 pounds though and 5'8", so different body types might not have such a sane strategy.