i think hes saying anyone could attack the mobs, but that they would be spawned by initiating the quest, the point of most open world quests is that everyone can participate.

So basically it would be like 100 raptors pop over the area, 3 or 4 groups kill the stuff, all involved get bonus sp, and some currency/fame/items or something.
kind of like a really large behest, but open to all, with a sp reward and no time limit.

its not a horrible idea, but how good it is will depend largely on how well its implemented.

or, maybe he does mean one group only