Starting with SSJ helps to provide the tissues malleability. However, you must warm up the tissues first. SSJ is like a good old stretch out before a jog, then a job before a run. In pumping, if you start out with a good SSJ after warming up the tissues, you're allow the internal tissues primed for a fast expansion through the first pumping. This is part of the "tricking your body" process."
SSJ mimicks a super hard erection, pushing the internal chambers to their max and slightly more. For brothers that are in their prime, or those who are still high on libido, your penises are pulsing like rockets ready to fly high. You're taking advantage of that initial rush of blood and nutrients sent to the penis. SSJ adds that extra volume of internal blood to the chambers, like extra rocket fuel while softening the tissues at the same time. Once you are ready to pump, you don't have to start at the baseline pressure but go straight to the higher pressure.
For those who don't like to go this route, we start with pumping instead. I'm one of them. I let the pump do the expansion with warm/hot water instead. I'm lazy.