Yes, the node normals are probably a compromise between all adjacent face normals that are attached to the vertex in question. By compromise, I mean average. Let’s say you have a vertex that is connected to three mesh faces, each having a normal. Its average normal would be the sum of the face normals divided by 3 (because of the three adjacent faces).
Now the faces can be planar, but the overall curvature can introduce torsion!
Check out this topic, where I get into why this happens and similar stuff is discussed: