This is in the same category as a limping wyrm. The game does not check against the possibility/impossibility of the generic afflictions but it does for the more exotic ones (such as "Tail chopped off"). WAD, though it is a bit counterintuitive.
I have wondered if mindless units can be the victim of Mindburn or Soul Slay, as they have no mind to burn, nor soul to slay. Further, what happens if you GoR a mindless unit? Do they lose the mindless attribute?