The horse has bolted
I don’t know whether to be charitable here and assume that it was a genuine mistake. After all of these different examples of stingy and incompetent landlords, its easy to assume that all of them are trying to pull a fast one when it comes to caring for their properties and their tenants.
If you look closely, you’ll notice that this bolt is fitted to a sliding door. Yes, this does mean that it’s completely useless, and yes, it does mean that whatever is behind that door isn’t safe. As I said, it’s possible it was a genuine mistake, I just hope that the landlord comes back to fit something more effective.