I don't understand something about this item. Unlike the Adamant and Lustrous Orb, we can't make a Pokemon hold the Griseous Orb because it's a Key Item. Is there a reason why or it's just a mistake?
1 - Adamant and Lustrous Orb
2 - Griseous Orb
Even if it's written "Hold Items", we can't put it on a Pokemon, you can try it yourself.