The Lati@site is in the XY code.
Remember that Mega Lati@s was first discovered in the coding for X and y, but was not released until ORAS. It can Mega Evolve because the coding for Mega Latias, Mega Latios, the Latiasite, and the Latiosite were originally made in X and Y.
![image](/pokebase/qa-plugin/https-img-proxy/image.php?key=849f01866ce7fca5&url=http%3A%2F%2Fwww.pokestadium.com%2Fassets%2Fimg%2Fsprites%2Fmain-series%2F6%2Fx-y%2F381-mega.gif)