Take those Eastwood "training" videos with a grain of salt. In many cases it's less about showing a proper way to do something and more about selling some gimmick tool. Looks like this is designed to make a valley of sorts so you still have a weld holding either side together. I feel this is going to have the same pitfalls as the flanged (lapped) repair that results in ghost lines showing in your final paint...
If you can practice with some scraps and get the welder setup to produce a full penetration weld, you don't need the gimmick tool..
