Don’t know if this is a bug or intentional. I’m calling it a bug for attentions sake.
The Dead Leg is a legendary class weapon that can be crafted w/o unlocking a lvl 60 feat. It and the arm are I believe the only weapons from the archivist that are craft-able before lvl 60.
Also, during my last purge I had 4 thralls equipped with the dead leg. None of them would use it. Instead they opted to use their fists.