I'm with you Bart, what this test proves is limited to the test.
But as far as the "overlap" being more with the glue, well, that is how it is used. The point being on a "pinch weld" on your average car, there are spot welds about every inch and a quarter or so. When you bond it, you apply the adhesive to the entire pinch weld area, much like my boy did here.
To make them "equal" in every way you would need to leave the welder unpluged being the adhesive didn't use any electricity.
The butt weld failed, not because of poor penatration but because the metal right next to the weld is the weakest point. This will be seen at any weld failure, IF the weld is well done.
Brian
