You may being refering to cutting the outside stops off and then putting the window in, I refer to this as "outside to in". If possible and of benefit when there are no inside removal stops or they are in pristine shape and you do not want to disturb them or the paint.
I charge $10 extra for "outside in" it takes a little more time.
That is how I understood it as well. 99% of our installs are "outside installs". Takes more skill/time, but does not disturb your interior which is one of the benefits of a pocket install in the first place. It also allows for a cleaner RRP install.