Yes. But my point was that this ought to be the default during development, IMO. I’d want warnings to block the submission of code, but not the compilation of code (and in particular not the auto promote feature!).
EDIT: Also imagine the experience for a newcomer who has just installed OCaml and dune following some instructions on the internet. Do we really want the compiler to scream at them when they write their first program and have an unused variable? There is undoubtedly value in being strict during code submission, but during iterative development, it feels very pedantic and IMO makes people focus on the wrong things at the wrong time.
EDIT 2: I also understand that being lenient is a slippery slope. Many users may ignore the warnings, and dune has no mechanism by which it could ensure that warnings are treated as blockers during code submission. So we may end up with more bad/buggy OCaml code in the ecosystem. But I fear that the price we will pay for being pedantic by default is that we turn off newcomers, and my guess is that the default might be so annoying that many experienced people immediately overwrite them anyhow.