I've taught that lesson a couple of times in Gospel Principles. I always covered the entire thing. Gospel Principles is a basic-level class, and the stuff might be new to people, so they ought to get the entire thing at least once.
Gospel Doctrine isn't a basic-level class, it tends to go deeper into portions of subjects and whatnot.
I think many teachers may also shy away from some of the parts because it will devolve the class into an arguement about whether the Lord hates vegans or not.
LM
(He doesn't, in my opinion...)