Have to agree with you to a point llanfairpg. Yes drivers, not just the student variety, have to be aware of all prevailing circumstances.
However, what was reffered to was a HGV learner. Yes, I am sure 95% of drivers would carry out an emergency stop to avoid the cat. Have you tried an emergency stop in 44t of artic?? Not pretty at best. If the conditions and speed are right, you have an even chance of your trailer overtaking you!!!
The point being made is that as HGV's are so difficult to stop when really heavily loaded that you need to think out of the box all the time. You develop a skill of being one step ahead of the vehicle at all times, second guesing what others are going to do, especially on motorways when the BMW is trying to get 3 feet infront of you. The same applies in the air, you need to be ahead of what the aircraft is doing by anticipating what's happening next.