The BATF looks ill on distributing information on how to convert semi-autos. As I said, I doubt that it was converted, but it could have been done with some radical reconfiguring of the fire control mechanism. It is not that easy to convert semi-autos to full-autos that are more functional than the semi-autos they come from.
A gun that fires only full auto can be created that is unreliable and difficult to control with a little less effort, but what would be the point?
You are correct a fully auto would only be effective in a crowded area with no other people being armed.