The rolling resistance of the ATs is probsbly not offset in a meaningful way with insets, wjere with the 21s it’s worthwhileI feel like Rivian made a smart move changing this in their production models to having a normal 20" wheel and having aero 21s.
The aero covers won't really make a difference on the 20s and some testing shows that they barely make a difference on the 21s being on or off so there really isn't a point imo