So.. As I understand the situation..
The material was removed from the connector in the new design to provide better mold release and precision. During molding, plastic parts must cool slightly in order for them to shrink and release from the mold. That void in the center allows the shrinkage to be more uniform and probably a little quicker. It is hard to get a solid plug or cylinder to shrink uniformly.
In Neutrik testing, both new and old components begin to melt after the same amount of time under the iron. They do not recommend you go beyond that point. It is about 10 to 12 seconds of heat (though it depends on your iron).
My impression is that the old connectors were more stable when taken beyond that point. Sure, the plastic may melt at the same pin temp. But a slice of butter melts faster than a chunk.
In order to maintain pin alignment, I recommend plugging in another connector to at least maintain alignment.