Yes, that is exactly what they are saying. Neither host nor custom/Macvlan networks even care about ports. Only a bridge network uses ports as has been explained several times.
Bridge mode uses ports for external communications. Although it is not necessary to do so, I setup OpenVPN-AS on two unRAID servers in my LAN. Since they are on the same LAN, I really only need to be able to connect to one in order to have access to the other, but I wanted to prove access to either via OpenVPN client was possible.
Being on the same LAN, they could not use the same ports. Of course, the OpenVPN-AS container on both servers is running in bridge mode.
On the second server, I assigned UDP port 1195 (what you are trying to do with 1200) to the second server and TCP port 9444 for management. Here are my router port forwarding rules associated with both servers:
I have a dynamic DNS name for each server and my OpenVPN client on my laptop has two profiles allowing me to connect to either server by DDNS name and the appropriate ports.
I rarely ever connect to the second server directly via OpenVPN as connecting to the first gives me access to the second which is strictly a backup server and is often not even powered on; however, I just tested it again and it works without issue on the alternate port of 1195.
Somewhere in your Open-VPN-AS container, VPN client, port forwarding rules, and/or DDNS settings, you must have something misconfigured. It is possible to use a port other than 1194 as my setup proves.