It wasn’t a widely used tag, and the pre-“deprecation” version of the page didn’t have much actual content, but to say that the recommended replacement is: man_made=works + product=machinery simply makes no sense.
I can’t see any discussion of the “deprecation”, so I’d be tempted to wait a couple of days for anyone to comment here, and then if no-one does, take that warning off the page and add a bit more documentation (as you have above!) to it explaining how the tag has been used.