Why are there shiny versions of shiny-locked legendaries?

Question

Why have them shiny locked, when they can just not have a shiny at all?

Answer 1

They will most likely be released as Shinies in the future.

Most Legendaries have been released in their Shiny forms via events, such as the Creation Trio, the Legendary Dogs, Jirachi, Mew, Genesect, et cetera. We can only assume that Game Freak programmed Shiny sprites for the likes of Xerneas, Yveltal and Zygarde for the sake of making them available in the future.

Comments

That makes sense, thanks!
This comment was commented 21 seconds after Astronautical answered.

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lol this comment was posted 17 seconds after you commented.

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lol, this comment was commented 8 minutes after you commented on my comment

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They also have shiny sprites for shiny locked Pokemon so if someone hacks a shiny say, Xerneas into their game, the game won't corrupt or anything :)

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But, if there was no shiny sprite, they wouldn't be able to hack a shiny-locked Pokemon.