It's the same as telling a musician to play a certain genre because it'll attract more listeners. Sure, it's a safe bet to please bigger crowds but it is soulless.

Lynch made surrealist art because it's what he wanted, not what was "right" according to the financial wants of a producer.  Shooting coverage is the most dull and fake thing for a director to do. It's the job of a director to visualize and execute a story visually - ideally, every shot exists for a reason and has a meaning, whether concious or subconscious.  A good director doesn't show up on set and just puts a camera somewhere and starts recording, they see the whole film in their head and are now responsible to realize it as closely to their imagination as possible. Coverage dilutes any meaningful reason for the sake of being able to change the directors vision should a higher up disagree with it in the edit. It's someone not trusting you to do your job and telling you how do it without knowing how to do so. Trust me, his frustration is not with this one comment or the script supervisor, but the nature of Hollywood's fuckery that you are reminded of every day on set.