Hydraulic discs are fine on steep hills, I have both GRX and Ultegra ones and they will stop you very fast. That’s on a much lighter bike though, and I doubt they’re putting Ultegra-tier bikes on cheap e-stuff.

Brake fade is a real issue, even with high end brakes. On a long hill, someone who's not comfortable with the speed will ride the brakes, just like inexperienced folks in cars do.

For a different definition of "fine." The problem with the steep hill and brakes for anyone will be losing control from either panic or over application.

Especially on a bicycle where you have a passenger onboard, high speeds are just best avoided.

Yes, but further into the article it seems to get more concerning - wheels falling off and brake failure, repeatedly.

It seems like there may be more to this than ‘just’ angry, bereaved parents.

It's pretty easy to get out of control on a descent in any type of motorized or non motorized vehicle on the hills in the area described when one has little experience. We don't prepare adults for this with cars or children with bicycles, a motorized bicycle however lets one dig a much deeper hole momentum-wise than one would otherwise be capable.