Why can't I forward ports used by "Separate" management interface ? ?

I ask this question quite a while back wanting to know if this was a bug or if it was working as intended (possibly a limitation of the chips ?) and never got an answer. 

Why does forwarding ports on the public interface affect the "Separate" Management Interface ? Or actually the other way around since the radio will not forward any ports being used by the management interface , separate or not...

Hi,

You can forward ports on both interfaces independently. There are two separate tables for that.

I don't want to forward ports on the separate management interface I want ports on the public interface to forward regardless of the same ports being used by the management interface. They are two separate interfaces with two separate IPs on two separate subnets, seems like it should be two separate sets of ports.

For example, if I enable DMZ  or try to directly forward port 80 or 443 (or whatever port you are using for http/s access to the management interface) or port 22 or any port being used via the management IP  those ports will not be forwarded.  Since you can't change the SSH port on the radio (that's a whole different complaint...) port 22 can't even be forwarded to the customer.  It seems to never fail that whatever port I use for the http on the management interface there will be a customer that needs that port or a range of ports that my port falls inside of... 

Also, seems weird that you can now forward ports on the management interface (where would you forward them to and why ?) and the public interface separate while at the same time being unable to forward ports on the public interface that are used by the management interface.   

Have I just missed some basic fact of networking ? Is it normal/expected that two separate interfaces on two separate ip's in two separate subnets can't use the same ports ?