If cloudflared is closed gracefully (i.e. its shutdown completes normally) then connections will be closed with Cloudflare edge. In that case, cleanup would not be useful.
However, if the shutdown is not orderly, e.g. a kill -9 is issued, then connections in Cloudflare edge will only close after certain TCP timeouts take place. During that time, if you try to reconnect, or delete the tunnel, you may get an error saying that you need to force that in order to overwrite existing active connections — which is possible with “-f” flag. An alternative is to issue the cleanup command before doing either of that with “-f”.
All of this is true because a given tunnel can only be ran once. If you want to serve multiple origins as a single entity (e.g., replicas of the same service across various machines), you should run multiple tunnels and place them in the same Cloudflare Load Balancer origin: https://developers.cloudflare.com/cloudflare-one/connections/connect-apps/routing-to-tunnel/lb