Populating Mesh With More Points Is Exponentially Slower, Not Linearly

Why on Earth?

By merely breaking it into three 3K point clusters with different random seeds, I could thus bring it down to 9 seconds, a whopping 3.7X speed-up.

Why, too, is there a bizarre pre-exiting population input P? What does that do, just forward them to the output, a silly thing, or somehow affect the population to avoid those point areas for new points? It doesn't say in the right-click help.