I wasn't looking at that recipe, just the sauce. The recipe sounds similar to one I saw Sam Choy put up somewhere. his has the pork wrapped in bananna leaves and then foil, so not sure what the water does except create a steamy environment in the oven. If the oven is between 175 and 200, the water won't boil (that's 212). I don't know about covering the pork with water without wrapping it first though, wouldn't much of the flavor leach into the water?
Edit - found the choy recipe