I have heard this often, that the glans gets very, VERY sensitive after orgasm in males, almost to the pint of discomfort, even pain. I have wondered what the evolutionary purpose behind this might be.
I have seen scientific video showing that, during orgasm the female's cervix will move toward and contact the opposite wall of the vagina, ostensibly to dip itself into the pool of ejaculate.
The only thing I can think of behind males' extreme post-orgasm sensitivity is to create a tendency to withdraw the penis and allow the female physiology to work.