Usually the brake master cylinder has two separate hydraulic systems inside it with diagonally opposed wheels on one part or the other (sometimes both fronts). It is really scary the the vehicle could lose all braking ability..
While modern vehicles they do have two separate brake hydraulic systems, they’re not separated by diagonally opposed wheels, but always by front brakes separate from the rear brakes.
I was driving at the time it happened. Luckily I kept control of the truck, and put it on the shoulder to avoid a wreck.
Afterwards, I had to extract the seat from my butt, but otherwise all’s well...