Don’t look down
When you rent a house or apartment, the very least that you’d expect is for the place to be structurally sound. You want to know that climbing the stairs, leaning against a wall, or opening a door isn’t going to result in something falling apart. No-one wants their home falling down around them.
If you have a balcony then you definitely want to make sure that it’s safe, and you’re landlord is responsible for that. In this case, the landlord did come out when his tenants were concerned about the safety of their deck, and he did take some action. I’m pretty sure that this wouldn’t meet any building code, though, and what happens when the dog runs into the plastic box?