Answer:
This unusual representation is due to the display factor for the deformations. If you set this factor to 1, you obtain realistic deformation without scaling.
The factor can be specified in the panel. The panel appears as soon as the results are available. You can also display it using the menu "View → Control Panel".
With the factor of 1, it is obvious that the force in the middle results in stretching of the cable. This stretching leads to an upward shifting of the outer nodes.
