The point the TRI was probably trying to make is that MEDLINK is a useful tool that you can use at any time, not just in the air. It came up as a discussion point during my upgrade training and the argument was that it does no harm to get the cabin crew to call MEDLINK while you are returning to stand. You don't know how long it will take the emergency services to get to the aircraft especially at some of the less developed airports we fly to and while you are waiting for them you (or the cabin crew as the case may be) are doing something useful. If the medics get to the aircraft before you get through on the satphone then great.
The point was also made that if you want medical advice about offloading a sick passenger before departure you can use MEDLINK for that as well.