Além de se referir ao Errata Corrige de 4 ed, pode-se usar esta regra opcional do Guia GM de 1 ed:
Rokugani Armor
In L5R, the system is fast, and the samurai who draws his sword often will find himself dead due to the devastating nature of the game. Below are a couple additional armor rules that GMs may include in their games to keep PCs alive a little longer.
Armor always adds to your TN
No matter what happens: full attack, backstab, called shot, etc., armor is always there. The abstract nature of the L5R combat system infers that no matter where a shot it targeted, the armor must be taken into account.
Neste caso, "Não importa o que aconteça" também cobriria os duelos de Iaijutsu, respondendo a pergunta com "Sim, a armadura aplica-se ."