Actually it does work and that was me who said it and have done it while at the South Pole as well as other places.
As I said before you have to use common sense when doing this. I said to melt some snow to where it is just turning to a liquid and pour the water onto the snow as you build it up around the bag. The water will freeze very quickly and give you strength. Once it freezes add more snow using common sense, and then more water. If you take a small zip lock bag and poke a few small holes in it, it will make it easier to evenly pour the water out over the snow.
Do not under estimate air pressure in a heavy bag at all. A good heavy contrators bag will not pop when snow is added evenly across it, and in reasonable amounts at a time. I build Monolithic domes and with two inches of water column or about 1/13th of a psi. air pressure I get almost two inches of concrete to stick to the top of a dome on the inside.
Sorry for the highjack, but I wanted to make myself clear here.