That is certainly not a very good way to repair that dropout.
1. I would remove a little more paint from the area than they did. Any possible contaminants near the weld area could cause failures in the weld.
2. Stick welding is not an appropriate way to repair that dropout. It will hold ok if you do a good job, but a professional welder would choose TIG welding for thin metal repairs. The other problem with stick welding is that there are a lot of sparks and slag produced during welding. The guy in the video did nothing to prevent these hot bits of metal from damaging the paint on the rest of the frame.
3. Welding outside is a risky process. People around without adequate eye shielding can get arc flashed and there is a greater risk of electrocution when arc welding. The grounding method through a bolt in the dropout was clever but besides that this is a hack job. The fact that he's welding on top of a stack of cardboard is also laughable.
4. There was no attempt to fixture the dropouts such that welding doesn't affect alignment. At the very least use a dummy axle, if not a full-fledged fixture, to keep the dropouts parallel!