What is a 'VPN kill switch' on mobile and what specific attack scenario does it prevent that a regular VPN without kill switch does not?

• A.A kill switch terminates every running application when the tunnel drops (the framework issues a force-stop to each package holding an open socket), preventing a crash report from leaving the handset unprotected: the scenario it addresses is an app that retries a request during the outage, never a leak of the real address, with an attacker disrupting the VPN seeing the handset go quiet
• B.A VPN kill switch blocks all traffic when the VPN tunnel drops or is being re-established; without it, there is a window during VPN reconnection where traffic flows unencrypted (a 'VPN leak' or 'reconnection leak') - an attacker who deliberately disrupts the VPN connection can observe the device's traffic or real IP address during the reconnection window
• C.A VPN kill switch blocks the client from moving between servers mid-session (the profile pins the tunnel to a single concentrator for the life of the connection), stopping an attacker from forcing a hop to a hostile exit node: the scenario it addresses is server substitution, always relevant on a consumer VPN with a rotating pool, never on a corporate deployment with one gateway