Just another thought, the approach plate has a SYD CTR frequency, they’re the ones clearing you for the approach.
The hard altitude is 2500’ that one should be respected by the G1000.
Should be 4 ways to do this :
- VNaV 3 degrees
- VNaV release the altitude, descend early to intercept the path
- Descend in Vertical Speed
- Descend in FLCH