That’s not a direct quote. The 50-75% is under a column labeled “Soil Moisture Deficiency,” not moisture content. It is a totally different measure, for farmers to use in the field without having to haul a 110degC +/- 5degC oven out to the field to bake a soil sample for hours.
Your right, though, in a way. Upon finding the actual standard, or actually, a more current version of the standard (ASTM D2216-98), it does define “water content” as the ratio of the mass of the water to the dry mass. But this definition is under a paragraph labelled “Definitions of Terms Specific to This Standard.”
So your definition wasn’t Bull S—, it just doesn’t have anything to do with HumanS—.
The quote from the medical dictionary says that, of the 100-200g mass of a typical turd, 65% is good ol’ H[sub]2[/sub]O. By the ASTM standard for determining “water content”, this would mean your nominal number 2 has a “water content” of about 186%.
65% water doesn’t seem all to hard to believe. Human bodies are about 2/3 water. Since most people I know are full of crap, this makes perfect sense.