Board Thread:General Discussion/@comment-101.165.195.170-20180717132827/@comment-35248429-20180809212408

Paralysis would stop a passive skill from working. The other answer is that kirito may just not have had battle healing at that time. They only have 10 skill slots after all, and passive healing is a skill that doesn't seem as usefull with great damage being delt later on.

Or it's an inconsistency brought out because The Black Swordsman was written after the original Volume.