I don't think the tele-convertor should have a spring on that tab. The lens does have a spring, so when the tele-convertor is connected to the lens the tab is put into the correct position to attach to the camera. If both the lens and tele-convertor had springs then there would be twice the resistance when the camera tries to set the aperture, leading to more wear and possibly even not having enough force to overcome two springs instead of just one.