It can’t be holding an item, since it’s in Home
All the moves currently on it are legal
Oblivious is a legal ability on it
Beast Ball is legal in Gen 8 (which checks out, since it has the SwSh origin Mark)
Level 100 is legal
The stats are legal if it has max IVs in every stat and an EV spread of 240 Atk / 16 SpA / 252 Spe
The only reason I could think it would be not be allowed is if it has an event ribbon or if it doesn’t actually have max IVs, and has an excess of 510 total EVs to make up for it.