I don't care what they call it, or what it is supposed to do, there is no attachment or bolt on, clamp on, glue on, weld on, tape on anything that will make a non walking foot machine into a walking foot machine. You asked if you would be wasting your money buying the attachment, and the answer is an emphatic yes.
When I was younger, I had a series of Volkswagens. The first thing I did was put headers on all of them. That reduced the back pressure from the stock muffler and gave them a little more zip. What didn't happen was the Volkswagen engine performing like a Porsche engine.
No one lives forever, the trick is creating something that will.