If you’ve played through Sun and Moon, you probably remember that at a few points you team up with Hau for a double battle. There are two important things to note about Hau’s AI:

• He’s aware of the additional effects of damaging moves and will try to take advantage of them.
• He will use his starter’s Z-Move if he sees a good opportunity.

However, he apparently can’t tell the difference between a damaging move and its Z-powered version. Meaning that if he sees both a good moment to use a Z-Move, and a good moment to try for an additional effect, he’ll think he’s killing two birds with one stone by using the Z-Move.

Meaning that if you have a burned Pokémon, and Hau has Primarina, he will try to heal your burn with Sparkling Aria. However, what will probably actually happen is that he kills your own Pokémon with Hydro Vortex.