#5 is wrong. The bar does not go straight up, it goes up and back. The bar starts in front of your body, but ends up directly over your center of gravity. It'd better, or you'll do a faceplant, so it has to travel up and back. Not sure what kind of cartoon physics the author is talking about.
I'll also add that the deadlift is the most injury prone exercise I've ever seen or done, and every time the injuries happen during multi-rep sets. My advice is, if you're pulling heavy stick to singles or doubles, and if you're doing doubles, do at least a partial reset between reps. Let the bar come to a full stop, brace that core, then pull again.