you can do them either but the reason i do them legs is you are using a lot of your lower body when you do dead lifts... really up to you. i consider them a leg workout even though deads workout much more. just like clean and jerk, its all in the legs where you get the power.
you gotta mold your workouts to best fit you, there isn't necessarily a right or wrong way .. I'm a big believer though in mixing things up. for example if you say you do 6 sets of exercise day A, then next time you hit those same muscles switch the order of those exercises. instead of doing everything in order each time. really throws the body off. so for example instead of starting your pull day with pullups, the next time end it with pullups. also pick a machine you never used at the gym and try that instead of doing the same things over and over again. I never draw out a strategy when i go to the gym, if a machine i was gonna use is occupied then i take that as a sign to try something else instead.