Not really new...
I've experienced the "standby upgrade" perhaps 3 times over the past twelve months. Asked at check-in and was told "maybe possible" even though I knew space was available. Once at JFK, for example, I was told to fill out a slip of paper authorizing the upgrade. Upgrade was eventually processed in the lounge or at gate. Just last night, my spouse was told to try on board!
IIRC, each of these experiences were at outstations, so don't know if it's partly a question of contract staff not having authority or not knowing how to do it without the EK supervisor.