It worked at first, then I remembered the landscape (level) I was loading had no foliage objects. It was just the landscape and my Playmaker system which was still instantiating the non prefabbed foliage. And of course the purpose of this is to be able to have thousands of prefabs sitting in the level ready to be loaded in the distance.
So I brought them all in, individual LOD's all set up so they won't even display when they appear (out of range). And there's a big pause while it loads. I didn't have the Async option ticked. So I tried it but nothing changed, instead it gave this message in the console;
LoadLevelAdditiveAsyc: _Scene-02
UnityEngine.Debug:Log(Object)
HutongGames.PlayMaker.Actions.LoadLevel:OnEnter() (at Assets/PlayMaker/Actions/LoadLevel.cs:54)
HutongGames.PlayMaker.FsmState:OnEnter()
HutongGames.PlayMaker.Fsm:EnterState(FsmState)
HutongGames.PlayMaker.Fsm:SwitchState(FsmState)
HutongGames.PlayMaker.Fsm:DoTransition(FsmTransition, Boolean)
HutongGames.PlayMaker.Fsm:ChangeState(FsmEvent)
_Scene-02 is the level being brought in, in the distance. The Asynchronous loading is supposed to load the level in the background so it can appear instantly, right? So this might be a bug, or is that not what the Async option is for?