… the BB gun and the AR have a different recoil pulse that will eventually destroy any scope not designed for that impulse.
Actually you are thinking of spring piston air rifles. These rifles (which should not be shot with BB's) have a unique recoil pattern. They recoil rearward then forward. The piston moving in its channel causes this. The other styles of air rifles and top end recoilless spring piston rifles don’t have this worry.
It is the forward nudge that can "unglue" the reticule in scopes built for traditional firearms. Traditional scopes do not provide reticule support for recoil in the forward direction.
This is becoming moot however, most higher end scopes are now built to allow this forward recoil, but it is still best to check with the manufacturer prior to using on the “springer” types of air rifles.
The Leupolds (and most other current quality scopes) will handle any traditional rifle that you are able to shoot from your shoulder. If I were in a gun shop who employed someone that said that these scopes would not stand up to a .300 WM, I would find another gun shop ... they don't know what they are talking about.