That seems wrong
We aren’t in the construction business, but we can tell you this is just wrong. Obviously, this staircase isn’t usable. When looking at the plan on the left, we can tell that’s not what the architect of this building had in mind. It’s too bad the workers who constructed this had the wrong idea.
Maybe the plan on the left isn’t designed properly, or maybe the constructors did a poor job. Or maybe it’s both. Either way, this staircase is clearly not functional. We don’t see any option other than breaking this down and starting from scratch; hopefully, with a better construction team.