I have done it to make the work go faster but I try not to for three reasons.
1. It is an incredibly dirty way to polish something compared to a Cyclo or other random orbit device. Just look at the guy. When you turn a polishing wheel at those speeds it throws stuff everywhere. Do not do it in your hangar. It will take you forever to get everything cleaned up. Wear a face shield, respirator and the oldest clothes you have or a set of coveralls that you don't mind throwing away.
2. The right angle grinders/polishers are heavy. After a day or two dancing with an angle grinder your hands and arms will let you know that they have been abused. Plus, they are pretty noisy.
3. Technique. He talked about light and hard pressure and heat. It is really easy to overheat a thin aircraft skin panel and cause it to oil can.
The only thing I would do differently from the way he is doing it is to hold the machine so the wheel is at a 45 degree angle (instead of straight up and down like he had it) and then on the next pass with the finer wheel and polish hold the machine tilted 45 the other way so the wheel is running at 90 degrees to the last pass. I have found the shine comes up a little quicker that way.
Does it work? Absolutely.
Does it take some skill to not damage anything? Absolutely.
Having done it enough on warbirds and other aircraft my preferred method for polishing anything is to find a reputable company and write a check. It is a nasty job.
is a good source for supplies.
Use the loose buff or maybe the spiral sewn wheels but whatever you do, do not use the sisal wheels. They are just too aggressive.
Use one wheel for each grade of polish. Don't try and use a single wheel for all grades even if you "clean" it between them.
Get a real wheel cleaner. Don't use a screwdriver or you might end up with a very shiny vaguely triangular device that is not good for screws anymore. Not that I would know first hand or anything.
To sum up. It does work but I can't stress enough how important it is to use a very light pressure and keep moving to hold the heat down.