I think it definitely can be a project thing. My experience with IWYU has been on very large codebases and I considered its ability to find transitive includes

I think it definitely can be a project thing. My experience with IWYU has been on very large codebases and I considered its ability to find transitive includes a blessing. The specific case where it shined for me was it made it much easier to identify the true impact of fileset changes on the larger codebase when it came to refactoring.