Here is what I believe to be the issue:
- In the first Kingdom Hearts Leon is portrayed as a 25 years old
- Birth By Sleep takes place ten years prior to the events of Kingdom Hearts
- This would make him 15 years old
- Leon’s resided at Hollow Bastion (Radiant Garden) during his early life
- New and returning worlds will be brought into Birth By Sleep. These include: Olympus Coliseum, Hollow Bastion, Sleeping Beauty, Sunset Horizons, as well as Destiny Islands.
- Terra carries a wounded Ven through Hollow Bastion
Exact quotes by Leon:
Therefore: I’m assuming a 15 year old Leon witnessed a supposed fight at Hollow Bastion (Radiant Garden) between Terra, Ven and the enemy; he was thrilled at the ability of Terra and/or Ven with the Keyblade, and so this is why he said the comment(s).