Creating and Editing Texture Coordinates (UVs) - An Introduction to Computer Graphics for Artists - page 160

Fig. 10.20 By changing the shape of the polygons so that they do not match the UVs, distortion
occurs despite having undistorted UVs prior to the vertex transformation
Fig. 10.21 The only way to ensure that textures are undistorted is for the polygons and the UVs
attached to them have exactly the same shape