« on: Today at 06:08:30 AM »
Focal length itself does not mean anything.
Focal length combined with sensor size (diagonal) determines the angle of view. Angle of view determines "telephoto compression"
So, 135mm on APS-C (1.6x) and 216mm on FF will give you the exact same "telephoto compression".
'Telephoto compression' and 'wide angle distortion' are aspects of perspective – the apparent size and distance relationships between objects in 3D space when projected onto a 2D medium. Perspective is determined solely by distance to subject – focal length, sensor size and AoV are irrelevant.
So your example happens to be correct, but the reasoning is not.