I think it's meant more as . . .
"The PCs can conceivably do anything the NPCs can. Take over a continent and usher in a new age of darkness and despair? Absolutely, but you have to form an army, raise the capital, fight your enemies, defeat the heroes sent to stop you . . ."
Same for things like becoming a god. Yes, the players should have the option to pursue that goal. No, obtaining that goal does not have to be easy. Yes, the GM needs to know how the PCs might achieve that goal, if that's what they want out of the game.