Hyundai and Kia added official GrapheneOS support to their apps months before Volkswagen banned GrapheneOS:
https://discuss.grapheneos.org/d/31697-myhyundai-app-has-official-grapheneos-support
Pressure from Volkswagen customers on them can achieve the same thing. There's no legitimate reason to ban GrapheneOS so they'll undo it with pressure.
myHyundai app has official GrapheneOS support - GrapheneOS Discussion Forum
GrapheneOS discussion forum
Leave a 1 star review for Volkswagen's apps on the Play Store asking them to stop banning GrapheneOS. Explain it's a far more secure operating system and fully possible for them to verify the hardware, OS and their app on it if they insist on doing it. It's far more secure than anything they allow.
GrapheneOS
Michael