yes that is correct. targets layby system does NOT allow prices to be overridden once they have been processed - there USED to be a manual process but since the introduction of their refund policy this doesnt/cant happen.
kmarts system ALLOWS prices to be overridden at any stage of the layby (prior to finalisation and collection)
bigw's system ALLOWS prices to be overridden at any stage of the layby (prior to finalisation and collection) as bigw have a "lowest price guarantee" their system automatically updates to the lowest price.