>>33983015I think it kind of assigns players a Pokemon. The set they showed on the official site is a Raikou with Electrium Z running Thunderbolt, Volt Switch, Shadow Ball and Protect. Probably not a set that most people would run, but sure enough, look on
https://bulbapedia.bulbagarden.net/wiki/Battle_Tree/Pokémon_(001-251) and you can find that exact set.
Also note, the Raikou is at level 80, so can't have been Hyper Trained, yet it has 6IVs. Also, it has a 252/252 EV set with no extra 4, which is Gamefreak's signature style of EV set for Battle Tree.
The thunudurus also has Wild Charge. Who uses wild charge thundurus?
https://bulbapedia.bulbagarden.net/wiki/Battle_Tree/Pok%C3%A9mon_(472-649) That's who.
Tl/dr they'll be Battle tree sets.