Ohhhhh, wow, didn't know that name would have been used. My bad, Thank you for clarification.

Its not about the object name. My mesh is named "Cube_HP" when exporting it as a .obj. But upon importing that .obj it to any software or blender its name becomes, "Cube_HP_Cube" , which I dont want. It never happens to fbx. Thats why its a bug.
Even if u have a single mesh in ur blend file with name having a underscore somewhere it will always happen something like this to ur mesh name.