Perhaps we can agree on the following?

1. Global Entry is a useful but restricted facility (specifically is only attainable by certain passport holders. Currently not Australian, although mooted for early 2025 - it requires application, fee, and potentially an interview (bookable appointments, can incur long lead time, but potentially doable upon arrival (did mine in Guam since no delay for interview and did my wife's upon arrival at SJC fairly easily on the only international inbound that day from LHR)).
2. It bestows TSA Precheck.
3. Those who have (I do thanks to my GB passport, my wife to another qualifying country's passport) enjoy both expedited passport control when entering the USA (potentially excellent when immigration queues are long) and TSA pre-check expediting security when travelling to or within the USA (of variable benefit depending upon differential queue lengths).
4. Global Entry can be typically entered on booking engines (Known Traveller Number - KTN). The system picks that up so that when you use the automatic kiosk upon arrival your flight details are already populated in the system.
5. Some airlines have the facility to enter Global Entry (KTN) in the booking details - sadly, QF typically has not.
6. Yes, remedy is to add at check in assuming staff can cope (some can, some can't) (FWIW I've done this at LAX first desk - others can get flustered eg. with multiple passports - the Global Entry system allows declaration of multiple passports)
7. Adding the facility to populate the data in the QF system would greatly facilitate - such would become compelling in the event that Australian passport holders start to qualify for Global Entry.

Now - if you are already travelling first class out of LAX and using the left hand escalator from the check in desk there may or may not be a great advantage to having Global Entry thereby TSA precheck since IME the priority line is quick (others can add assenting or dissenting experiences).

Global Entry becomes compelling upon arrival since the self service kiosks entry where allocated bypass any queues - such may it be a issue depending upon location and time of day.

Renewable 5 years - may or may not need an additional interview depending upon personal case assessment.

FWIW with family in LA we wouldn't be without it - but we're lucky to have passports which qualify...