Maybe you are talking about different things? The normal AirPod has a fixed shape - it either fits your ear canal or it doesn’t. You definitely should try it out before buying it.
The AirPods Pro has changeable sizes, so it really shouldn’t fall off anyone’s ear.
Couldn't get my AirPod Pros to stay in with any of the tips I could find. Tried silicone, foam, all shapes and sizes, different amounts of pressure and depth in ear, but nothing worked. They'd just slowly creep out and eventually drop out, especially if I spoke.
Regular 2nd gen AirPods are like glued in though, I could headbang or do handstands and they wouldn't go anywhere. Go figure...
In my experience the fit can be very dependent on the precise orientation in the ear. When I get it right they almost never fall out, when the angle is off a bit they hold for a few minutes at most.
I haven't tried the AirPods yet and the shops around here (remote Atlantic islands) don't have an unboxed pair for me to try. From my experience the Pro models would work fine but the other models will probably fall when I am doing work in the woodshop or doing yard work. I have maybe three or four in ear headphones lying around that didn't fit the bill. For some people, that type of headphones don't fit.
The AirPods Pro has changeable sizes, so it really shouldn’t fall off anyone’s ear.