Consider the following…
There are literally no pictures in between Diantha’s Hall of Fame picture and Ash’s. This leads me to believe:
A. Diantha attended the camp last year.
B. Diantha is currently 11 years old.
C. Ash needs to stay 10, because in the Poke World, you become full grown once you turn 11.
D. A year in the poke world lasts two decades in ours.
E. That kid with the Pangoro is a badass.