Just tried selecting Auto DR and initially I only got options of DR100, DR200 & DR400. Aperture was 1.4 & shutter speed 1/125. I then selected Shutter speed to A and Auto DR was available for selection.
This has to be a bug, right? It just makes no sense tying it to shutter speed. If I have the ISO set to auto6400, and my f stop and shutter speed are such that the camera selects a high ISO, then I would like for it to auto select DR400.