There is a difference between an air fryer and a convection oven. An air fryer has its heating element in the top with the fan so it is actively blowing hot air down on the food. It's basically a convection broiler.
This right here. A lot of people saying ugh it’s just a convection oven, but they have a weak fan blowing from the back of the oven while the heat source is at the top and bottom, 8-10 inches away from the food. In an air fryer the heat source is only a few inches from the food, and the much more powerful fan is right behind it, blasting the hot air down and through the food. And the small size means no warm up time necessary so it’s far cheaper to run.