My example is not about "omitting the final explicit destructor", it's about forgetting the final explicit destructor. That code block can die in at least two places ($dbh set to RaiseError, or $elapsed being zero) and then never call the destructor, leading to memory leaks and/or unreleased locks. Creating the lock-release right at lock acquisition prevents such oversights, and having to disable each and every such instance is foolish.