Isn't the whole point of NGCI to automate the system? I expect that the baggage system would sort the WP, SG etc. into separate bins to load and offload the aircraft, reducing manual sorting.
Received my silver card and tags yesterday as my SC review was the end of October. If the silver and platinum look similar I guess the level of mixups will increase.
Also with paper labels it would be easier to notice a misplaced bag - for example a solitary bag labelled SYD on a trolley of other bags going to PER.
I can also envisage the tags falling off in time as the rubbery straps that loop around the suitcase handle perish. The one off plasticised paper labels were single usage and were more resilient than the old QF credit card type ID labels with plastic loops.