From what I've heard, stepping up only grows enough yeast cells for the volume of each step. To properly step up you must do a step, decant off the fermented wort, put the majority of the yeast in sanitary vessel (jar) while leaving some yeast behind to ferment the next step.
What I've been doing lately, with much success it doing starters (well, and starter over the 1mL that my flask can hold) in my 5 gallon carboy. Stick it in the fermenting fridge to cold crash the yeast, decant off the fermented wort, and then pitch the yeast into the larger carboy when the time comes.