Not to mention that, if everyone does this, the water pressure will be decreased where the fire trucks need it. If the fire turns out not to threaten your property you’ll feel like the worlds’ biggest jerk.
Actually, no where does he advise against it. Did you even read the comments? He said "The sprinklers could have helped, but I just see solid defensible space. Trees are limbed up, grass is maintained, no dead veg on the property, no trees taller than the roof that would put litter into the gutters."