The original post has nothing to do with the curvature of space time, or non-Euclidean geometry.
This only has to do with the fact that on a plane (e.g floor of a building, of literally any size), above a gravity source (here, we can treat the earth as a point source), the gravitational vector will only be perpendicular to the surface at a single point. All other points will experience gravity at an angle.
The original post has nothing to do with the curvature of space time, or non-Euclidean geometry.
This only has to do with the fact that on a plane (e.g floor of a building, of literally any size), above a gravity source (here, we can treat the earth as a point source), the gravitational vector will only be perpendicular to the surface at a single point. All other points will experience gravity at an angle.