The points here are about how it makes it easier to design such games (except for #4 which is the only valid reason for certain types of game). Also, the control thing isn't that big of a deal. Even earlier FPS games had quick switching to alternate between two specific weapons. It shouldn't be that hard to come up with a seamless interface to speed up the access of weapons without having to restrict the player to just two. Again, it is fine for designers to do things that make their job easier but they shouldn't be dressing it as something that is fundamentally better, because it doesn't actually improve the player experience and in many ways limits it.