Covid has created an anomaly in that immigration was stopped so its a distortion of what would normally be the case.
The reality is that before Covid under the Coalition we had climbing under employment then the covid anomaly happened impacting both the unemployment and underemployment rate. Under-employment rose during the years of the coalition govt.
The issue is covered comprehensively by the Reserve Bank Of Australia(RBA). The RBA chart below shows under-employment increasing between the Coalitions 2013 up to the time Covid hit.