Great advice. I remember back in the 80s the bike mags saying not to extend your inside knee like motorcycle racers do because a bicycle is not a motorized vehicle and the dynamics are different. Keep your knees together normally. Yet today I see cyclists do it. A bad habit or a change in thinking? I believe the intent was that you need to keep your centre of gravity away from the inside so keep your hands on the drops and your legs in.
Oldsters may remember the Avocet slick tire ad from the 80s featuring this famous photo of Jobst Brandt:
cozybeehive.blogspot.ca/2010/03/jobst-brandt-part-iv.html
It was used in full page ads to quell concerns the new treadless tires weren't safe for cornering.