Hello!
It's already implemented, and even in a more flexible way. Since a few months ago linking a name to a specific port is no more pro-forma only, provided that you have multiple "devices" and you configure different ports to link to different "devices".
You can link the port to a specific "device", and a specific DDNS to one or multiple ports. In this way you have an even more flexible and comfortable system. For each device, each name of yours will resolve into the exit-IP address of the last VPN server to which you connect through that specific "device". In the port panel just select the "device" you want for that port, provided that the port is enabled. You can do so in the combo box just under the enable/disable toggle.
If you use the same "device" on multiple devices which connect at the same time, and/or you have your remotely forwarded ports configured to "all devices", you will experience the behavior reported by @ddrahos , i.e. you will fall back to the a behavior which allows full backward compatibility with the previous system.
Kind regards