"Five-Man Band" Questions

I know these questions have been asked before, but I'd like to know:

Looking at the trope page for The Leader (and The Hero as well), there is no described requirement for The Leader or The Hero to be male. And on the pages for The Lancer, The Smart Guy, and The Big Guy in all three cases they discuss how those roles can be filled by females. Yet, on the page for The Chick it says that the role MUST be female, and if it is a male then it is The Heart.

So why is that the other four roles are described as being possible for either sex, but The Chick can only be a female?

Also, is there any difference between The Chick and The Heart other than that The Chick is always female, and The Heart can be either male or female? Isn't that kind of redundant then? Why isn't The Chick just merged with The Heart?

We have a thread dedicated to the cleanup of this trope, here. The definition is not up for debate, but you can read more about the reasons for it there.