In addition to the other benefits already mentioned, the SS1 makes it simply properly rinse the inside of the BC bladder.
You simply unscrew the SS1, fill with water through the corrugated hose, swish the water around and dump the water out.
Better still, the SS1 thread is the same as a standard garden hose. To rinse my daughter's BC, we unscrew the reg and attach a hose and let it run a few minutes. She has 4 "OPV type" dumps and the water flushes out through those. It looks like a lawn sprinkler.
I dive BPW/s and all my air cells have a single OPV. I have a corrugated hose that has the female SS1 adapter. It is easier for me to swap corrugated hoses and a attach a garden hose than it is to rinse through my standard inflator after a dive.
Zeagle makes a standard inflator that is similarly threaded and can be removed for rinsing the BC