As far as the OW policy goes, luckily nothing has changed when it comes to guesting, unlike Star Alliance where guests cannot be on a different flight since 2021:

“Emerald and Sapphire members may invite one guest to join them in the lounge. The guest must also be travelling on a flight operated and marketed by a oneworld carrier.”

That being said, AY is in the wrong here when it comes to +1 guest. They can however make up their own rules when it comes to family access or Lumo guest allowances.