My reasoning, which didn’t make it into the final edition of the previous post, was the following: the equipment in question is a passive property of a mercenary itself, not the ability that it modifies.
In my opinion, it often reveals sloppy and inconsistent (done in an ad hoc fashion) coding behind the scenes. I’ve reviewed an instance of in on the forum — in my opinion, it tells about even more mess behind the scenes than meets the eye.