When writing in loosely typed languages, some folks aim for 100% line coverage, to make it more feasible to refactor down the line. Which then of course ends up being a lot of tests for fairly basic stuff that the type system could help you with...
I think such tests are pretty useless regardless of language. If you work on say a banking system testing whether getBankingStatement() returns something of type string is a waste of time. It just slows you down when you refactor its return value to a BankingStmt instance. While testing what happens in low memory conditions when a user simultaneously deposits and withdraws while another user issues a charge back against them is extremely useful.
line coverage but also branch coverage. Every safe navigation operator used in "defensive" coding, ex. `foo?.bar` is actually another branch that needs to be covered if that's the metric people are using. All of those tests are unnecessary in a language where the type is known at compile-time.
My experience with folks proudly proclaiming "100% coverage" is that it's typically "just" line coverage, even if you're obviously right.