It seems it’s the same problem than in Rotation and scaling of child not preserved properly when parent is non-uniformly scaled and rotated or Distortion occurs when the mesh is moved from the world coordinate system to another non-uniformly scaled mesh - #2 by Evgeni_Popov.
The outcome is that we would probably need to support shear deformation in our transformations, but this is not something we plan to do, as it would represent a huge change in the code base. Handling non-uniform scaling is always a problem and should be avoided if possible…