Just stumbled across this thread while doing some research of my own. One thing I noted was, while perusing the Graves Registration Field Manual, is that the coordinates on the Report of Burial are the geographical location of the cemetary, rather than the location of death. I really wish cause of death on the IDPF I received was a more clear. It states "M.W. Body". I am assuming multiple wounds - body, but haven't been able to find anything to verify this.
I believe that goes to the purpose of the IDPF. It's primary function is to track the disposition of a soldier's remains. Thus details like the exact location of death or even the exact nature of wounds were not considered a high priority. Also, as you have touched on, often the abbreviations used were not consistent. However, I believe your intuition is correct regarding what "M.W. Body" means.