The watchdog process is spawned bare (no link/monitor), so if it crashes its failure goes unnoticed, and if pfcp_peer restarts the orphaned watchdog may fire a stale cast at the new process.
The watchdog process exists solely to send a delayed message to pfcp_peer on timeout, and to be cancelled (by receiving heartbeat_response) when the response arrives. That's exactly what erlang:start_timer/3 does natively - no separate process needed.
