The old design, found in Knysna, belongs to the UK-family of signs (see Great Britain). It doesn't come as a surprise given the country's history.
The new design is omnipresent, shifts away from the UK-family and is much closer to the worker from Germany. But again the blade of the spade is not entirely sunk into the heap; the German worker drives his spade much deeper. It may very well be that roadworkers in Africa have learnt to proceed with more care. After all in this part of the world you never know what may surface when you push a spade in a pile of dirt.