>>52222632>they're not the normThere is canonically more than one Moltres, Zapdos, Articuno, Mew, Deoxys, Regirock, Regice, Registeel, Shaymin, Manaphy, Phione, Diancie, Zygarde, Cosmog, Cosmoem, Solgaleo, Lunala, Type: Null, Sylvally, Meltan, Melmetal, Zarude, Kubfu, and Urshifu.
Some mons aren't being added simply to keep things simple-it's theoretically possible to make more Mewtwo, but wether it's canonically happened in-game is heavily debated. Logic follows that Regieleki and Regidraco should have duplicates somewhere across the world like the original trio, but this has yet to be proven, so far all we know they were made specifically for Galar.
It's not the "norm", but it's not uncommon either.
