Or he could do it with a proper load balancing proxy such as HA Proxy. Then he would be able to take one node-instance down gracefully, update it to a newer version, and put it online again (and repeat for all other instances).
Another benefit would be more fair share of the load (not every request will take the same amount of time to complete).
I'd agree that a balancing proxy is more appropriate for HA. The post mentions that this is specifically not intended as a high availability solution. It's a fairly narrow use.
I've used this trick to forward to a Twisted Conch daemon running as a non-root user. However, I would never consider this approach for load balancing.