I’m currently not using Atmos at all, but my understanding is it’s fine with side wall speaker placement.
Consider that the ‘ideal’ is for overhead placement, but not too many people have ideal arrangements.
Bill has cathedral ceilings with his overheads and they work fine. The AVR will adjust for distance and delay as necessary.
More importantly, as I stressed before, is to just make certain those speaker positions line up as best as possible with the diagram. You
do not want them on the front and back walls as height or presence speakers. Properly placed, they will put you in a bubble, so to speak. As long as your bed layer (front, center, surrounds) is set up properly, those elevations will give you that effect.