Board Thread:Speculation House/@comment-85.130.101.225-20130816112245/@comment-3146930-20140722220835

Jaune's Semblance may have activated out of reflex as well. If he had trained as a kid, but his father gave up on him, he would have little reason to try and continue his training (as shown by his lack of combat knowledge, including something like Aura). If he was never in a situation where his Semblance was needed, then it wouldn't matter if his Aura was unlocked or not. It wasn't until Cardin was about to land that finishing blow that Jaune's Semblance activated to protect him, allowing Jaune in the future to use it more effectively because he knows what it is.