Agree the approach with spirits is really poor and has been for some time, especially in SYD. Though to be fair, think I've only ever once been denied a double shot.
Just the other night was proactively offered a double Dalwhinnie 15 in MEL.
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Perhaps just to finish off the bottle. (Hopefully not their last).
Never been denied a Bloody Mary or (in the past) an Old Fashioned - but I guess these fit the aperitif ethos.
As others have said, makes no sense from a RSA perspective, nor costs. I recall a discussion with the MEL F&B manager a few years back where he said QF management simply didn't prioritise securing spirits over other airport lounges.