@Adam Griff
Literally every background pony student at the School of Friendship is an adult model.
Also Sandbar’s body template is the same as young Burnt Oak in the perfect pear, who is Bright Mac’s best friend and we can assume pretty close to the same age. The same age Bright Mac gets married at. Just because he’s twinky doesn’t mean he’s like 13.
“Minor” might have been the wrong word to use (given how subjective it is) but they’re not children.
They’re clearly meant to be younger, yes, but if they show wanted to illustrate them as kids they’d make them CMC-sized. I think the young six are clearly in the 17-20 range.
But she’s smaller than Ember and other female dragons she’s obviously younger than her and female ‘background’ dragons about the same size as Grable Who was said in Dragon Quest to be a teenage dragon she’s a minor by default and all the others are clearly younger in their respected species.
Sandbar looks more similar to teenage ponies we’ve seen than adults.
Ocellus next to other changelings is noticeably smaller indicating she’s young she resembles teenage ponies in size.
Gallus is smaller than other Griffons that we know are adults and isn’t much bigger than Gabby so they can’t be too far apart in age.
Silverstream is basically the same thing with sizes not matching (also she needed a permission slip sighed by her parents if she wasn’t a minor she could just sign herself)
And Yona again size doesn’t match the adult Yaks and her horns are smaller than older yaks. She’s also the only one I have an argument in favour of being or at least close to being an adult during her holiday story she says her family braided her hair for the first time which may be a coming of age ritual for yaks
True other characters have been shorter like Short Fuse but have characterized that make them similar to adults like being more muscular.