It was a pretty thorough study:
> Our study is the largest to date in the literature: we generated 31,000 test suites for five systems consisting of up to 724,000 lines of source code. We measured the statement coverage, decision coverage, and modified condition coverage of these suites and used mutation testing to evaluate their fault detection effectiveness. We found that there is a low to moderate correlation between coverage and effectiveness when the number of test cases in the suite is controlled for.
Given their data, their conclusion seems pretty plausible:
> Our results suggest that coverage, while useful for identifying under-tested parts of a program, should not be used as a quality target because it is not a good indicator of test suite effectiveness.
That's certainly how I approach testing: I value having a thorough test suite, but I do not treat coverage as a target or use it as a requirement for other people working on the same project.
[1]: https://neverworkintheory.org/2021/09/24/coverage-is-not-str...