Game Mechanics: NPC with One Weapon not Punching

[Handull]

Was just fighting a skele in HS north that I assume had been used as a pet, since he was duel wielding two slashing weapons. I disarmed him once, knocking out his primary, but his secondary was still equipt. At the end of the fight the skele quad-slashed me. I was shocked to see four "slashing" messages in a row, since he was technically fighting with a fist+slash. I didn't think to check if he was punching me at all during the fight, but I could always check logs. Not sure if this effects the dps output of uncharmed npcs, but it seemed like a bug to me. I'm assuming it will be easy to reproduce.

[Sunderfury]

Resolving as a lot is speculation without logs to back up and lack of repeated occurrences. Could be a number of other reasons why this legitimately occurred.