>>42158165The anime based it on Gen1, were you started your Pokemon journey aged 10.
I think general canon is that you can own Pokémon at any age, but you have to be at least 10 before you're allowed to 'compete' competitively.
This goes for officially sanctioned Pokémon Battles, Contests and other forms of wider entertainment.
A bit like how you can play gambling based games at any age, but official gambling events and establishments have an age limit. You can gamble at any age, but can't take part in official events until you're 18.
