That would be a great limitation, if only you were entitled to serve as gate keeper for the English language. But the fact is that the term mechanical computer has been a part of the language for quite a long while.
I have never heard of a mechanical computer other than the Babbage Engine and the mechanical naval artillery computers. The navy computers are clockworks that have position and speed settings for cams and the like.
You are not the gatekeeper of the English language either. Most techies would agree with me; and, we are the ones who specify and make those sort of devices.
Some people call magazines "clips" and refrigerators "ice box", but that doesn't make them right.