Slop.

mechanical linkage to the electronic booster system afaik. instead of using vacuum pressure from the combustion engine, these cars use an electronically controlled booster with a master cylinder that pushes fluid out to the calipers

to be fair, hydraulic brakes with power steering dead would be a tall order to stop a fucking 3000 kg rust bucket too

I had a tiny ford focus power steering fail on a muddy, but flat road and it was pretty scary

If the ABS was faulty and fighting him, or the power brakes failed, there is 0 chance for a human to stop a 3000 kg truck rolling down a 26° slope, even with perfect grip. Whether it has hydraulic or fly-by-wire breaks, if the electronics were faulty it wouldn't matter.

I've had to stop my 2000 kg van from 110 km/h, on a relatively flat surface, when the ECU shat its pants in the rain and the engine died. Let me tell you, I weigh 80 kg, never skip leg day, and yet it took all my strength for a good 20 seconds whaling on the service brake to stop it (and yes, I made sure to let off a bit when a wheel locked). Add another metric ton or a steep hill and it would basically be impossible for all practical purposes.

Not totally sure for the brakes specifically on the truck but I know wayyy more than normal is fly by wire in this shit. So wouldn't surprise me at all