From a couple of OTBs that I’ve witnessed, I’d say that ”loose cargo syndrome” is a main contributor to this kind of accident.
Rider clamps down on the brake w/o having braced him/herself against the bar properly. Bike stops, rider’s body continues forward, and drapes her/himself over the bar as a sack of potatoes. And the bike topples over.
I don’t see it as a brake issue, rather a skill issue.
First bike tour I did was on a canti bike. Almost ended badly one cold, rainy descent when I simply couldn’t pull the lever hard enough.
Now, with hydro discs, two fingers will stop anything.