I've been intrigued by this concept and am wondering why it improves accuracy. Is it some magic derived from the hollow cavity or is it because that in the course of swaging the tip you are also expanding the nose of the bullet a tad thus making it more of a bore-riding design. In the world of cast bullets in rifles a long-ish nose that firmly rides on top of the lands- the bore- is more accurate than a bullet whose nose doesn't and relies solely on the base of the bullet to engage the rifling. I'm wondering if that's the case here?

"You can lead a man to logic, but you cannot make him think." Joe Harz
"Always certain, often right." Keith McCafferty