You are correct. The advantage is that I could revert back to the jug on the front of the Natures Head for collecting the liquids if I need and then circumvent collection of the black water liquids in the gray tank. I see it as affording me the best of both worlds. If I have collected urine in the gray water tank I plan to dump at a designated dump site. That is not to say that once urine is collected in the gray water tank I will forever thereafter dump the gray tank at a designated dump site.
I should mention that I have never dumped my gray water on the ground or any place other than a designated dump. I might need to in the future, but to date, I haven't needed to.