I may make one obvious observation. Every time it happened - there was a female driver behind the wheel.
I am insinuating nothing. I am simply observing the facts.
There's nothing in TCHs to prevent hydraulic brakes from engaging, except the ABS system. Folks somehow fall into belief that regenerative braking is some sort of hybrid voodoo, while in reality, any harder pressing on brake pedal engages hydraulic brakes right away.
The only time you will need to "put entire weight" on the brake pedal is when you have catastrophic system failure, with lost power assist. Just like with any other car, that has brake assist, and loses it.
I can see it happening when all the lights come up along with VSC and "check hybrid" warnings, otherwise - something's not right....