This "Export to" also does not include any ESC config or Components related to RealityKit. Does Apple suggest to newer again use AR/3D Quick Look with interactive content again, but instead handle all use cases with a Spatial Preview Application or custom built Reality Apps? these would exclude iPads and iPhones. If so, an official statement / tutorial would help

I assume the ECS config and Components should be done als over in the main layer. i wonder how maya handles foreign schemes

Wouldn't it then be needed to also add the "old" ARReferenceObject to the list of Anchor types in Reality Composer Pro? AR Quick Look still supports it, when a scene was created with Reality Composer. See feedback FB15552682