I think he’s saying he’d scan the film so he can edit it digitally, but then conform the camera negative to the digital edit. So basically how films were edited after NLE software became commonplace but before digital intermediates were a thing. Or, in other words, how Christopher Nolan works.

This was actually taught in some of my editing and finishing classes in college. After teaching us how to edit 16mm film using a razor blade and tape. (The year after I graduated they switched to 100% digital…)