QF15 departs at 11:30am daily
EK BNE Lounge is open for the three EK flights a day:
EK434 - 5:30-8:30
EK435 - 18:00-21:00
EK433 - 23:30-02:30
So unless you want to get there really early, to be kicked out at 8:00ish when EK434 is boarding/ed - it isn't an option many would choose.
Plus you do have the 8-10 minute walk down to gate 75, only to have the same walk back for the experience that rules it out alone for most.