Leon watched that whole exchange showing a calm expression. He imagined that he would feel enraged after hearing all that. However, after confirming his theories directly from Ilyana's mouth, he felt… strangely calm. Although the fourth Leon's reaction was justified given the things he had to see and experiment with, Leon could understand him but not react in the same way.
"I guess a lot of things makes sense now…" Leon muttered. "I learned magic fast and developed my skills faster than the others because I experienced the same training more than a few times… thus, the knowledge of how to learn certain spells and skills came naturally to me."