4s + 1

I have some difficulties explaining (and understanding) the 5S. Do you think that the fifth "s" is essential? I mean, if you standardize, the 3 previous S (and the whole system) become sustainable.
For educational purposes, it would be simpler and more understandable to program, implement and evaluate the performance of the first 4. If people maintains the area and items, simultaneously sustains the new order.
?
I agree that is necessary to add a 5th activity to avoid kickback and maintain the improvement (sustain). 
But: 
1) The subjects for the 4 first (initials) S are workpeople in genba and, in any sense, the 5th is in charge of the supervisor. Is kinda meta-activity to assure the continuity of the standardization process. Not the same kind of action. 
and 2) Why, after standardization we don't begin the improvement of the process? Why consolidate? 5th could be the continous movement of the wheel. 
So, this is my model for the "4s + " lean tool









I think it is sufficiently expressive and reflects my idea about the topic.
5th "S" (Sustain/Improvement) is the engine that keeps the wheel running. 
The owner should belong to management staff.
I think it won't be part of the visual control in cells. Better in Obeya.



Manuel J.