I watched a video where this lady did the math and went over the BTU and efficiency of various ovens along with the air fryer.

Actually they're not convection ovens. They're Impingement ovens. Convection oven move the heated air 'around' the oven. Impingement ovens blast heated air directly down at the food.

So they're not a scaled down convection oven. They're a scaled down version of the pizza ovens restaurants have.