Yes you need to be competent. Used to be part of the old advanced course along with a bosuns chair not sure if it is still in but for sure theres a separate course.
Swing stages come under the Aus/NZ regulations.
i'm sure theres a seperate ticket for cradle work and it comes under the riggers domain also i would have thought it verges on the need for a LOLA inspection ticket at the least as its a mechanical device lift a man, the same as it would it would be for a hoist,although its possible that seperate manufatures training as a competant person would surfice