The foot is on the footrest or the floor in front of the brake when not in use. Honestly. I don't understand why people here have such a hard time getting that. Maybe it is difficult for you. It is not for me.
That's probably the real issue. How far does a vehicle travel at 100kmh in the time it takes you to lift your foot off the footrest, over and on to the brake and apply pressure. With a very real risk of leaving your right foot down.
Versus lifting off the throttle, over and down. As I said, if you've never had an incident, then that's testament to your current driving. But there is probably data somewhere showing performance of such a test.