scaling a mesh won't change its shading

Sorry if this may be something obvious, but i’ve been blocked by this for a while, but couldn’t find anything on this in the documentation:

New scene, with a single directional light. The high cone in the back is shaded correctly. The low cone on the right is also shaded correctly. They are both imported as .fbx (All meshes have “mobility=movable”)

But the low cone on the left is a copy of the high cone with its z scale set to ca. 0.1. It retains the much darker shadowing from the unscaled high cone.

So i guess the question is: Why are the shadows on the meshes not recalculated when i scale them?
Of course, when i rotate them the shadows update properly. it’s just the scaling that doesn’t change the lighting.