Mjb
All AAV HEMS have the ability to take two stretcher patients, although the second is put fore and aft in an elevated position on the stbd side and has limited access for inflight care.
It is just as important to get the cas to a trauma centre which has the capacity available. Your example of going in opposite directions indicates that (probably) The Alfred could only take one whilst the second was assessed for an alternative trauma unit.
I've been one of two 412s that went to The Alfred from the same incident with a cas on each; and each one needed intensive work by the team on board all the way. You'd need a very large cabin to manage that with two stretchers and two teams.