To my mind, computer-chess refers to the chess games played by computers (or rather engines or chess-computers as you noted), so they are referring to slightly different things. So probably the questions should be re-tagged because one of the tags has been misused.
I noticed computer-chess is frequently misused on questions about programming engines. I do not see why we need the slight distinction between games between engines and discussion about engines, as how an engine plays is an integral part of discussion about engines. I believe the tag should just be a synonym for engines as noted in the question.