Of course if you focus on one muscle and do tons of volume for it you will get a huge pump... that comes from the high volume territory (metabolite build-up, oedema).
It's a totally different approach. It's not for everybody. It depends on your psychological profile and what you expect of a workout. Does it work as advertised? YES! But if the lower pump bothers you mentally it might get you less motivated to train and thus get less results