1. So when you press the purge button (which is pressing on the diaphragm) the air RUSHING/GUSHING OUT of the second stage mouthpiece is at ambient pressure? Is that why it is rushing out so quickly bubbling all the way out like a fountain and isn't coming out at intermediate pressure and is subsiding as it moves away from the valve opening? The intermediate pressure just COMPLETELY and utterly goes down from 140 psig down to 0 psig ambient instantaneously? Is this what you are saying?
That IP air is at pressure when it is contained, i.e. in the hose. Once it gets past the remand valve the velocity increases with expansion and there is some locally higher pressure as it diffuses in the case but this is in no way full IP. What you represent as full IP is more like force, the combined effect of some pressure combined with velocity.
Statement 1 of post 3 is at best poorly worded.