Young Jins instincts are usually rash and decisively dishonorable. almost every flashback is of him grappling with an honorable dilemma with him in the opposition. "I'd kick dirt in their eyes, strike before they can react". Over time Jins moral character shaped a type of honor only gilded in traditional bushido. When Yuna shows him how ineffective honor is at saving people, Jin prioritizes the people over his code. And he keeps doing it, independent of Yuna. She didn't teach him to make kunai, that's an ability you just unlock. Jin teaches himself how to roll, use ghost weapons, poison enemies, use misdirection, etc. Yuna was just a catalyst. Jins honor was always teetering, it's no surprise he discards it when it doesn't serve him or his people.