Have you ever tried to shoot a light bulb outside at night, without clipping the highlights, then recover the shadows around it? If there are not a lot of details in the shadows you will see the sensor noise (not banding). I can assure you if you shot this exact situation with your 5d3 or 6d, recovering the shadows will give you this result. Its not in the dual iso image because thats what dual iso was designed to do. To give you better highlight and shadow detail.
These ML iso options will be a great advancement in the mysteries surrounding canon iso and cleaner, better iso.