If, and that is a big "if", the regulator and operator are honest in their processes, the use of standard weights for larger aircraft usually is adequately accurate ... if the system skews the procedure, it's anybody's guess ...
The cited FAA AC standard weights are, I suggest, significantly out of date and current analyses would suggest that they need to go up a bit ... my comment is based on studies done in Australia some time ago and presume that the US and Australian populations are sufficiently similar in the extent of obesity to draw such a conclusion.