Hm, that line should be updated in the documentation, as that's not entirely true. It's fine to use a reverse proxy or load balancer in the case of Portal HA.
Aside from the fact that it's a best practice to put Portal behind your firewall and conceal its machine name, standard ports for URLs are 80 and 443. I'm not sure if you have another component you'll use to send traffic from 80 to 7080 or 443 to 7443, but it won't lend itself to be a clean user experience if you don't have something in front running on 80 and 443.
