Aren't most movies that are in the dual aspect shot by the camera so you don't have to have it jumping from one aspect to another?
I didn't see Aquaman in the local cinema to know how they handled it because they are usually 2.40:1, at least that's our local.
most multi aspect films are shot to be “safe” in CinemaScope, meaning you can mask it down without missing any required on screen detail. Even avatar is safe as well.
BUT, seeing something like the chase scene in the dark Knight on a full screen is a completely different experience to seeing it cropped on CinemaScope.