The “image ignore” and “client ignore” flags are meant to IGNORE the mac address in use for the respective item. For example:
Image Ignore makes it so the MAC Address being loaded is NOT going to be able to be used for Imaging. But this is only regards to the system it’s registered with. (Seeing as identity is verified/validated by the MAC Address this should be expected).
So, an unregistered machine, using a NIC that is registered to another machine, will appear to be that “registered” machine. Why would Image Ignore be a useful option? I don’t know, but I know the client ignore option IS useful (for example a shared USB nic on multiple machines so you can have the client work without thinking the system is another host.)