The internal NIC, mvneta1, sees traffic from the switch on port 5 exactly as if it was an external switch.
So an interface assigned as mvneta1 directly (as LAN is by default) will see untagged traffic.
You would create VLAN interfaces on mvneta1 and assign them to see the tagged traffic arriving on each VLAN.
Since it's working I assume that's what you have done.
Steve