They seem to be saying that by pulling up you’re likely to be less focused on the other foot pushing down which is MUCH more important.
This is true, but only if your unpractised in.
you pull up with one leg and push down with the other one at the same time . By aiding the foot pushing down you can spin it more easily /faster surely ?
Dr Broker seems to miss the point that you don’t try to use equal power pulling up, just a bit extra to maintain the circle at the top and bottom of the stroke.