I was like you once and believed a convection oven and air fryer are the same thing and produce the same results. But I was wrong!
There is a subtle but crucial difference between an air fryer and a convection oven. A convection oven only circulates air around inside the oven, keeping the steam trapped with the food, while an air fryer actually removes all of the steam away from the food, allowing it to get much crispier much faster than is possible with a convection oven.
You are kind of right though, because now that air fryers have become popular, they’ve started marketting small toaster-oven-style convection ovens as “air fryers”, even though they legitimately are not air fryers and do not cook the food the same way that an air fryer does.
so an air fryer is more like a small convection oven?
if you want the steam to escape, you can just open the oven door for a few seconds and there it goes.
also the air circulation is more intense in an air fryer, and it’s a smaller enclosed space which is easier to keep at a high temperature. both of these also help food cook more evenly.
I wonder if I could DIY an air fryer with a heat gun, a metal box, and a PID controller.