I’ve now read the start and end of the explanation and here’s my conclusion: this proof ends too soon, it just shows you can generate a lot of heat to melt something you put in contact with it. It doesn’t show how you get to technology from a melted bit of metal. So because of that I’ll consider the challenge to not be fulfilled yet, but this can serve as the basis for a later explanation (I’ll assume the explanation for getting thermite is correct for now even though I did not have the time to read it and evaluate it).