Fuji,
I think you are confusing the EBS with STASS (short term air supply). EBS is a simple rebreather device which will give enough time to egress and get to the surface. All NS passengers have EBS now. See
Shark Survival Home Page - Air Pocket. STASS is the mini scuba system as you put it and is a variation on diver's spare air system. STASS requires more training and runs the risk of baro trauma.