I downloaded this model from here and noticed that the sharp seams that are created for those models do not have any effect, because I print screened the right-most image after I cleared all seams and nothing changed. Why is that so?
Can’t say for sure from the cropshots and without the model, but my only guess is that the model was imported with custom normals, which override auto smooth angle and sharp edges.
Sharp edges aren’t seams, clearing seams won’t do anything.
Turns out it was an Edge Split Modifier.