Pulled means shredded, and that the meat is falling apart done and tender, sliced means just that, like sliced roast beef or prime rib. Bythe way Chuck comes from the front of the beef, the shoulder and neck area.
Certain cuts of meat have alot of connective tissue, Chuck is one of them. It is the "pork butt" of beef. meaning the shoulder area.I cook chucks as large as 26-28 lbs . The breakdown process takes as long as it needs to convert the tough meat into tender goodness. Often times a 5 lb chuck will take as long as a 12 lb chuck. Its the time for the process to work,not the time for the meat to come to temp. Thats why we have the stalling out at certain temps.That when the energy and heat make the magic happen. I am not saying that 1.5 hrs per lb is wrong, but if it was right, those 26 lb chucks wouldn't be getting done in 14 hrs , would they!
Flintlock, enjoy your learning/smoking experience. Its a ton of fun.