Why we should put this limit? On past Nation Cup we never speak about this...
Well, you kinda brought it up by referring to Dunga and Yeon. Besides just because the first edition didn't have that rule that doesn't mean the 2nd can't have it. In sports rules gets changed too to try to improve things. I'm not saying the rule should be implemented or not, but there is no reason to do it the exact same way as the first time when you can do it in a different and maybe better way.