"This footage is the result of somebody obtaining these animations early, which is why you see Hoopa using Thousand Waves and Volcanion using Thousand Arrows – the animations do seem to suit those of Zygarde if you look closely."
In short, they got the animations, not pokemon with those moves legitly. Verified by the fact that the Volcanion has Light of Ruin, AZ Floette's Signature Move.