I've noticed while watching clips on YouTube that the Shadow Giratina other people encounter have Giratina's theme, while mine has the regular legendary theme. I have Giratina in the front of my party, but I tried switching it's position in the team and even boxing it, both of which didn't work.
I did see one clip where a guy had Giratina in his party, although not in the front, but I've also noticed that all the clips I've watched are from 2 years ago :/
If I had to guess, there was probably some update that changed the music for some reason. Either that, or the fact that my Giratina is shiny somehow affected the music.
So, is there a logical explanation for this? Or does a specific ILCA employee hate my guts?