It’s as simple as the subject describes. Works for .stl, but not for .obj.
Why would one need .obj instead of .stl ?
Stl files do not contain custom vertex normals, but .obj files should. Custom vertex normals help avoiding shading artifacts when CAD models are rendered in external render engines.
They use a different work environment, STL&obj is generally used by design, manufacturing and production usually STEP/igs/X_T, these formats.
@zw3d_liangfen I never saw your reply. I understand what you are saying and I am well aware of the use of different formats.
The chord height tesselation tolerance is a setting specific to the .obj file export, so I am not exactly sure why you mention STEP and other file formats, where such a setting would be utterly useless ?