Both yields include fat loss in trimming. They are based on what I purchase at and the final meat I serve.
These are the numbers I use and I have found to be accurate for me. They are slightly on the safe side, you may get 5-10% more.
Also, that is for packers on the brisket. Flats only have a higher yield, less fat.
Grab a kitchen scale and start weighing after purchase, after trimming, and then after it is ready to be served. You can't really go by post cook weight on the butt because you will lose some fat and the bone once it's pulled. Chopped pork get's a better yield because most people chop the fat in there which is one reason why I like to judge a place by their pulled pork.