I cannot for the life of me find the original announcement for the ironhands upgrades back in 2003.
We all know ironhands makes one much much harder to parry than normal.
I am positive that unarmed defense was given the same bonus but not anywhere near as strong, and it's not in the helpfile, and it's not mentioned in the helpfile for ironhands explicitly either. It says assassins don't match up but not that assassins get a similar bonus.