Dart,
In fairness to ATC, those two items are mandatory readbacks. You have to readback frequency change instructions and clearances:
AIP GEN 4:
4.4 Read‐Back Requirements
4.4.1 Pilots must transmit a correct read‐back of ATC clearances, instructions and information which are transmitted by voice. For other than Item a., only key elements of the following clearances, instructions, or information must be read back ensuring sufficient detail is included to indicate compliance:
a. an ATC route clearance in its entirety, and any amendments;
b. en route holding instructions;
c. any route and holding point specified in a taxi clearance;
d. any clearances or instructions to hold short of, enter, land on, conditional line‐up on, wait, take‐off from, cross, taxi or backtrack on, any runway;
e. any approach clearance;
f. assigned runway, altimeter settings directed to specific aircraft, radio and radio navigation aid frequency instructions;
Note: An “expectation” of the runway to be used is not to be read back.
g. SSR codes, data link logon codes;
h. level instructions, direction of turn, heading and speed instructions.
Item F may also include the SYD LLZ freq...