Choice items not working?

Taen’s Gallade is supposed to have a Choice Scarf, but he’s able to use Zen Headbutt followed by Ice Punch. Why isn’t the Choice Scarf working properly?

There’s a weird bug where on rare occasions choice items don’t force the user to use the same move. It’s been around since ZO but hasn’t been fixed because the cause is unknown and seems inconsistent to reproduce.