As someone that has recently taken an infant and and family CPR class for my son who started solid foods a few months ago, this is pretty similar to how they teach it today and I'm pretty sure it would have the same effect. You can't perform a heimlich on a baby or very small child for a variety of reasons. This method or something similar to it is both safer and more effective, since it lets gravity help dislodge the food.
Maybe, but if true it means that whether the child is choking on feathers or bowling balls, they are ejected at the same speed, which is a great advantage of this technique.
Way back when my oldest was little one, he was choking and I just grabbed him and flipped him upside down and kind of bounced him like you're trying to get ketchup out of a bottle. It worked and I had no idea what to do, it was like an instinct kind of thing.