What other benefits does ND have inside other than letting you shoot wide open?
Most lighting equipment for film isnt really made for shooting at these incredibly low levels. I almost always stick a .6 or sometimes even a .9 ND on LED Panels I use indoors for night stuff (sometimes even during the day), because it just is impractical and tedious having to work in the 1-5% output range of these units. Same goes for tungsten fresnels, at ISO 800 and a t1.4, you can do very little with even a 300W without completely blasting the scene with light. Having everything on dimmers and constantly in the "barely on" region makes fine adjustments very difficult. Also, this isnt a bright, high key kind of look, but very dim shots - so if you shoot this at an 1.4, every tiny adjustment can become very strong.
An additional benefit of giving yourself some headroom in terms of having an .6 ND on the camera is if you shoot a lot of commercial work, as Patrick evidently does, the agency at some point will tell you "we love it ... we just wondered, if its possible to have it just a bit brighter". Often you can get out of these situation with a bit of reasoning and explaining to them, that this was the look that we all agreed on and so forth, but if they are stubborn you can say "sure", change to an .3 ND on the camera, stop a bit down and you can immediately offer them a version that is a lot "safer". If you light precisely to the level that you think you will need and give yourself no headroom at all, this would take a longer relight.