Just one mathematical point: 7 x 3% annual increases is not the same as a 21% increase.
e.g. $100,000 increased by 3% is $103,000. $103,000 increased by 3% isn’t $106,000. It’s $106,180. Do that another 5 times and you don’t get to $121,000.
However, the overarching point that pay increased by CPI does not maintain the ‘buying power’ of pay is unassailable. Even the ABS acknowledges that (or should I call the ABS “The Other Bureau”…).