I believe Art Jones started calling the pullover the upper body squat, probably in the early 70's. One of the reasons he designed his pullover machine was to increase the potentional of that exercise. With the point of resistence on the the elbows, it was taking advantage of better leverage. With Jones's designed cam on his machines, the strength curve was brought into better action throughout the exercise. After you finished a set of pullovers you did a set of close grip lat pulldowns. The lat bar was positioned above and in front of you on that machine. You could get very strong on any of Jones's machines but it did not transfer over when going back to regular BB/DB training. But you could get more muscular gains. In my view the BB/DB is the most effective tool (so far) for gaining functional strength and muscle size for the average person.
When adding the BP with a set of pullovers (pullover & press) you have a winning combination for upper body mass, in my view. Dip's (weighted) are also a outstanding upper body mass builder. Though using 400+ in the BP since I was 19 I have always gotten better results (development/functional strength) with weighted dips as have a lot of my Bud's. Good Luck.