React Flux dispatcher vs Node.js EventEmitter - scalable?

When you use Node's EventEmitter, you subscribe to a single event. Your callback is only executed when that specific event is fired up:

eventBus.on('some-event', function(data){
   // data is specific to 'some-event'
});

In Flux, you register your store with the dispatcher, then your store gets called when every single event is dispatched. It is the job of the store to filter through every event it gets, and determine if the event is important to the store:

eventBus.register(function(data){
   switch(data.type){
      case 'some-event':
            // now data is specific to 'some-event'
         break;
   }
});

In this video, the presenter says:

"Stores subscribe to actions. Actually, all stores receive all actions, and that's what keeps it scalable."

Question

Why and how is sending every action to every store [presumably] more scalable than only sending actions to specific stores?