Re: Why wasn't he paying attention?
"not least because I can get my foot onto the brake pedal more quickly when it's flat on the floor in front of the brake, "
You'll spend as long lifting and placing it as if you were on the loud pedal.
I tend to set my foot just above the brake pedal when using ACC. It's extremely useful on country lanes where you can get on the brake that much faster when some idiot comes round a blind bend on the wrong side of the road, driving too fast for the conditions.