I was playing around in the Festival Plaza in Sun and Moon searching for people to battle with, and I got challenged my a random Japanese person. I accepted, chose a team and stuff, and the battle begun.
It was a pretty normal battle... until the very end. He actually send out a (Japanese named) shiny Nihilego. When I saw it, I was pretty confused since I knew the Ultra beasts in Sun and Moon are shiny locked. As far as I know, there is no way to get a shiny Nihilego, not even through event. I didn't knew much about it, aside from two moves being Power Gem and Sludge Wave. It also didn't have a hacked ability, it had just Beast Boost.
I didn't obviously know any of it's EV's, IV's or Nature either, but can anyone tell me if I was right? And if I'm not, how did this person obtain a shiny Ultra Beast?