So...Giratina initial CP was bugged?

A friend of mine was lucky enough to catch his first Giratina with a weather boost. It had over 3000 CP (which i thought was too high). He tried powering it up and it dropped to 2400 so it seems it was a bug but he was angry as hell. It was hard trying to explain that apparently Niantic used pre nerf stats since he is a pretty casual. I hope this can help ease the minds of some others that feel they did something wrong and ruined their mon, you are not alone it was just Niantic being Niamtic again