It's highly possible as their fists are implemented using a modifed unarmed weapon. I'll have to test this when possible. Thank you for bringing this to light.

Edit: While I haven't tested it extensively from what little testing I've done, both Star Platinum and The World seemed to exit combat when I used weapon disarm on them although I'm pretty certain that they merely dropped their fist weapon and were unable to pick them back up. I tested this with both just the first word of weapon disarm and all three after that.

So it is possible that you've somehow got a mod conflict despite this being a relatively simple mod. However it is still possible that I'm wrong. If anyone else could test this as well I would appreciate it.

Yare Yare Daze