What ever happened to the old "slow down, then speed up" routine? Throws the dog off-speed. I have whippets and greyhounds, which can top out at 33 mph. Not saying it isn't scary when any dog takes up the chase, but I can't imagine any dog running faster than a moving bike, unless you're still in first gear.
This is actually good advice, the dog will change the intercept angle based on the slower speed and won't be able to react quickly enough to the increase in speed. But on the flipside, who wants to have this as part of their ride prep everyday?!