I echo your thoughts that Client will use a different port (of its own) to connect to server every next time.
But the ports of BO services that Client will connect to will be unchanged till the time BO services are not restarted next. I am just using these ports list to know services behind them. As in the BO service that are using these (random assigned on server)ports.
The end objective is to apply RequestPorts on all the services coming into picture while communication over firewall. But I agree Admin Guide has this covered very well.
Thanks 