Guess it’s different because there were injuries in the bus, which I wouldn’t have expected from just braking

I would have. When you slam on your brakes what happens? You go forward in your seat. In your car you’re restricted to how far you go by the seatbelt which locks to prevent you going too far. People travelling in buses tend to not wear seatbelts so they’d have flown forward and directly in front of their faces would be the metal bars of the row of seats in front.