I was not directing my comment to your coworkers. I was just arguing that a documentation can only be out of sync if the method's intention is changed. And if an existing method intention is changed, your problem is not the out of sync documentation, but the fact you probably broke something in your existing code, not in the years to come, but today.
It is about people. In the world where team members last ~2 years and move on, expecting that documentation is left not updated is in my opinion perfectly valid assumption.