Burning question

The thing that has me confused about hair removal in general is that several clinic representatives have told me that when an anagen phase follicle is treated it is dead forever. They also agreed that while some follicles may not become active until later in life, we are all born with a set amount. I’ve read many posts on this site and others saying that they have had the same hair grow back with little or no improvement.

Here’s the burning question:
I realize that results may vary as far as overall effectiveness of any type of treatment based on the patient, equipment, and experience, but can anyone say that it IS or IS NOT true that one particular, properly treated hair follicle is forever dead after being lased/IPL’d during its growth phase?

Are these people experiencing regrowth experiencing it on the SAME hair follicles?