Dual Identity Credits

If a character has two pages (for example, Dick Grayson and Batman, Wally West, Barry Allen, and Flash, or other characters who have taken up a mantle), should both pages be credited or only one? And if so, which one? Thanks.

I just got into DC and from what I can tell both are credited. After all, Batman is in the issue and so is Dick Grayson. I'm not sure what that this is how it's supposed to be done but it's definitely what is being done.

Thanks.

Recently I've just been crediting both.

I actually keep reading it as that, and I posted this!