I've never heard that before. I almost always hit mine with the hose to remove blood and hair. It also helps cool the carcass.
My wildgame butcher (35 years experience and also a hunter) does not want the meat getting wet (including washing off blood) and then hung. He says it "increases" the likelyhood of bacteria and can cause premature spoilage. He requests that the animal simply be drained and hung, but if you must clean further use clean dry rags or papertowel to wipe it off. I have always gone with his advice.
My wildgame butcher (35 years experience and also a hunter) does not want the meat getting wet (including washing off blood) and then hung. He says it "increases" the likelyhood of bacteria and can cause premature spoilage. He requests that the animal simply be drained and hung, but if you must clean further use clean dry rags or papertowel to wipe it off. I have always gone with his advice.