Not necessary that the walls casted from the inner face of column are a mistake. This can be the architectural demand and consideration. Also if u observed closely . The cantilever projections are coming out from columns ends directly . This removes the possibility of beam in the front face . Since it is a small room this will have a direct flat slab supported by columns on all four sides. .. this is a side of the picture too . This may or may not be true but this too is possible ... if u understanding.