Is it how the wing3D model is supposed to look ?

That's a little trick I use sometimes to transfer edge weight with obj, by relying on vertex normal to define where the crease are supposed to be.
The idea is to split the vertex into points based on vertex normal attribute, create a group with the open edges, and on this edge selection I create the crease attribute the subdivision method is looking for, re-weld every points and apply the subdivision operation.

So yes it's a way to save crease in .obj, but I don't if this method is really reliable.