In case you weren't aware dependent on what your threat model is and reason for using a VPN on iPhone, iOS 16 does communicate with Apple services outside an active VPN tunnel. Worse, it leaks DNS requests. #Apple services that escape the VPN connection include Health, Maps, Wallet.

The Lockdown Mode leaks more traffic outside the VPN tunnel than the "normal" mode. It also sends push notification traffic outside the VPN tunnel.

This is also the reason why VPN clients like IVPN and Proton have removed their iOS app kill switch features.

This was discovered last October and as yet I am unaware of Apple addressing it.