Yes, mathematically telephoto is exactly just cropped wide angle. The same light field is falling on the front element of either lens so, modulo focus effects a

Yes, mathematically telephoto is exactly just cropped wide angle. The same light field is falling on the front element of either lens so, modulo focus effects and distortion, it could not be otherwise. (Differing projections/distortions such as fisheye are likewise exactly equivalent to mathematical transforms for the same reason.) You can see that this is true when using a (physical) zoom lens. When zooming, there is no change in the projected image of any sort other than it simply grows larger. The effect you are referring to is complementary to parallax and is likewise due exactly to physical proximity to or distance from the subject being photographed. (Telephoto lenses require the subject to be further away to remain in the frame; in doing so, they move relatively closer to the background, thus longitudinally compressing the scene.)