During the 2024 Teraleak it was revealed all character models in Pokémon Masters EX are scaled to fit into a set of categories with minor adjustments for each character.
The categories are:
- Child
- Boy
- Girl
- Man
- Woman
- Man (Tall)
- Woman (Tall)
- Special
"How accurate in size are these models?"
Sadly, these aren't made to be scale-accurate.
Here's a comparison between all of the characters with a "canonical" height (from sources coming from concept art and the like), and as you can see it's not consistent between characters.