>>58223012 (OP)
Reminder that in the Pokemon world at 10 years of age you can:
>Travel the world without parental supervision
>Own a magical creature that can shoot an elemental burst from their mouths or cheeks
>Gamble on magical creature battles for real money
>Gamble in a casino
>Become the Champion of a region, who presumably has some level of political power, if not as the leader of a nation as someone on the upper echelons of that region's power structure
>Become a Gym Leader, who serves as a cornerstone of a city's community, economy, and tourism as well as someone who has official duties to face criminals
By this logic, a 10 year old in the Pokemon world being legal is a logical conclusion because if they can make these kinds of decisions, then they are clearly aware of what sex is, what the consequences can be, and thus we can also infer that Pokemon humans mentally develop far, far faster than our world's humans. This would make sense, considering Pokemon grow and change so quickly, and since Humans and Pokemon CANONICALLY IN THE GAMES used to be the same species, it makes sense that humans would have a similarly accelerated growth, and their greater physical endurance and wellness at older ages (i.e., Lusamine is 41+ years old but looks like she's in her 20s) we can also assume that Pokemon humans can remain in their prime far longer (which conveniently explains why ash never seems to age!) as well.