When they're talking spray, they're talking industrial strength spray from firehoses... not using a pan or bucket full of water—which is pretty much my point. Most boats I know of won't have a proper source of heavy water spray to extinguish with... most would try and use a bucket of water, and that can be a big mistake.
The reason they specifically mention spray is probably two-fold, the most important being that spray will absorb a lot of the heat as the fire tries to vaporize it, dropping the temperature of the fire quite rapidly and helping prevent additional materials from catching fire, and it also dilutes the alcohol, and due to the volume of the spray, does it rather rapidly by increasing the proportion of water throughout all of the spilled alcohol in a way using a bucket or pan full of water can not.
Just remember most hard liquor will burn quite well...and a lot of hard liquor is only 40% alcohol by volume... so you need a lot of water to dilute alcohol to the point where it won't sustain a flame.
Also, how well do you smell the alcohol if it has spilled and made its way down into the bilge... where it will evaporate off and possibly leave an explosive atmosphere? If it isn't right after the spill, you may not detect the odor of alcohol sitting in the bilge.
BoatUS's position on alcohol stoves is that pressurized ones are far more dangerous than the Origo-style non-pressurized ones. A pressurized alcohol stove can leak fuel in many places, and the leaks aren't always visible. A non-pressurized stove is safe as long as you're careful to wipe up the spills, the tins don't leak, and you wait until the tins are fully cooled before refueling them. The number of alcohol stove related fires has dropped with the disappearance of pressurized alcohol stoves as a common appliance on a boat.
Most people underestimate the risks posed by alcohol as a fuel. AFAICT, you haven't corrected the post I was responding too, which I've quoted here.
My boat has a pressurized alcohol stove. I was not thrilled about it when I bought the boat because they have a bad rap. The previous owners had converted from Propane to Alcohol. I've heard that with Alcohol, you can't see the flame. This is only true if the flames are in bright sunlight. If the flames from your stove are in direct sunlight, I think the battle is probably lost already! Besides, the flames from the burning fiberglass should be highly visible by then The good news is that if a alcohol fire gets out of control, you can put it out with water, and the vapors are lighter than air and therefore evaporate Quickly
(unlike Propane). I can get fuel at any hardware store. It may be a little slower to heat than Propane, but I am very happy with the Alcohol stove and oven. I don't think it should be a deal breaker, there are bigger issues when buying a boat. I would certainly try it for a while before replacing it. I think Alcohol is fine.