Dry weight, to my understanding, also includes no Battery acid on models without sealed batteries.
The reasoning behind shouting out a "Dry" weight is marketing. "Oh, look, we weight one pound less than our competitor!!!" Granted, the needed engine oil may actually put then tweo pound more than their competitor, so they post the numbers that make them look good. The realy number you want to look for is the wet weight... not that they publish that anywhere...