I am not doubting the leave for the medics and fight through, However, once you have fought through and recovered the injured. Then you have to get them back. There are not too many medics stretcher bearers in the British army to have one per injured soldier, so the section must help them back to a point where they can be treated fully. This can be upto several miles away and to tactically move several miles with an injured man takes time. As you also say it depends on the circumstances.