I don't believe that the manufacturers of medical equipment test their IEC sockets for insertion/detachment forces, having worked in destructive and non destructive testing before the NHS I could recommend some test equipment.
If the IEC connector is pulled straight out then it could prevent equipment being pulled over, however I am sure that many of you have repaired items that have been damaged when the IEC connector did not pull out. If my experience is anything to go by, you have also had to repair units where the IEC socket has pulled out of the equipment.
Retaining the mains lead would be more to do with the problems of having the correct size and type of mains lead with the equipment (and preferably the one that the equipment was tested with); as well as the incessant demand for replacement mains leads because staff have lost or removed leads (and the problems of do you retest as the mains lead is changed, who pays? Do you replace the batteries? Has the configuration been lost etc).