Yes, those URI patterns are accurate. The intent is the members of "NetworkPorts" within "NetworkInterface" will point to the NetworkPort instances underneath Chassis. So, your "NetworkPortCollection" underneath systems will look like this:
The same is true for NetworkDeviceFunctions. The reason for this is to allow for complex types of designs where physical ports and functions can be shared by multiple systems. So, in order to prevent duplication of resources, the collections under a given system will ultimately point back to their physical representation under chassis. I think we can add some additional language in the descriptions in NetworkInterface to make this clear.