I get that Nintendo wants to discourage hacking, but shiny-locking legendaries isn't going to help. Most hackers probably know about this and will either hack to get the shiny, or will simply avoid the shiny forms. Every legendary has a shiny form, and it doesn't make sense for one to exist if it isn't even possible to get. Out of the 3, Xerneas is my favorite while Zygarde's looks like it's trying to copy Xerneas (which doesn't end up looking good) and Yvetal is just meh. I wish they were available though, and I hope there will be some sort of event to unlock them.