Ok, so I have not used them befor but just incase I fancy a quick last minute get-away how does lounge access work on these tickets?

Lets say I rock upto the airport 1.5 hrs before departure and buy a standby voucher for a flight. I decided to wait in the Koru lounge until time to report to desk. Alas, I swipe my RFID however the gate Beeps RED on entrace as I have NO confirmed flight for the day... Is this correct or what is the story???