[mickmate]

The watts stops the forward back movement at the otherwise unsupported top of the hubs. If the axle breaks it is also the top arm for these rears and it collapses inwards. The watts does nothing for that. The radius rods are usually designed to work in tension. They don't have enough cross sectional area to work as a column. Your bike wheel hangs from the top spokes, if it was standing on the bottom ones they would collapse.