I'm no expert when it comes to Piaget's stages of development but what I did learn is his age categories are generalizations. Take the "Formal Operations" which aligns with adolescence, a lot of teenagers don't meet this stage until much later and this is partly why they struggle so much in college classes. But most will full fill this stage by the time they are sophomores in college. So it stands to reason that if many are later in development than others can be earlier.
DD is advanced in the stages.
