I believe that "Specialization Restriction" had to do with whether an artifact was a "sword" or a "bow" but it didn't do anything, or make a difference one way or another.
iirc it was meant to tie in with the whole "unit type" idea, such as melee, ranged, special etc. I've never bothered with it, but it may not work correctly if a melee unit picks it up, and it is set to "Bow" for example.
Thanks for the Info guys. I was able to talk to Myrd on hotline, and he confirmed what lothar said. It does absolutely nothing. The dialog had Sword as bow as options, but choosing 1 meant nothing.