Just guessing......You're probably extending your hips as you punch for the pike, and that extended position shifts your weight slightly forward. When you shift your weight forward it gives you a feeling of "balance" as you elevate, and it's that balance that allows you to initiate the pike motion.
I call this a balanced set because it puts a brief brief moment into the take-off where you can get into the right posture as you leave the floor to initiate either a twist or a salto. It doesn't really balance like a ball on a seal's nose, but it does allow for better control.
If you don't have a balanced set for the tuck in will allow your shoulders to lead the skill and "fall back" as you extend out of your punch. This creates a bad situation because your legs, specifically your shins, have to "catch up" before they start circling your traveling center of gravity.