NetworkInterface.getHardwareAddress can return zero length byte array when run with preferIPv4Stack

$ cat ListHardwareAddresses.java
import java.net.*;
import java.util.*;

public class ListHardwareAddresses {
    public static void main(String[] args) throws Exception {
        Enumeration<NetworkInterface> netInterfaces = NetworkInterface.getNetworkInterfaces();
        while (netInterfaces.hasMoreElements()) {
            NetworkInterface netInterface = netInterfaces.nextElement();
            byte[] addr = netInterface.getHardwareAddress();
            System.out.format("%n%s : length %s", netInterface.getDisplayName(),
                                                  addr == null ? "null" : addr.length);
        }
    }

}

$ java ListHardwareAddresses

Software Loopback Interface 1 : length null
WAN Miniport (L2TP) : length null
WAN Miniport (SSTP) : length null
WAN Miniport (IKEv2) : length null
WAN Miniport (PPTP) : length null
WAN Miniport (PPPOE) : length null
WAN Miniport (IP) : length null
WAN Miniport (IPv6) : length null
WAN Miniport (Network Monitor) : length null
Microsoft Kernel Debug Network Adapter : length null
RAS Async Adapter : length null
Oracle VM Virtual Ethernet Adapter : length 6
Oracle VM Virtual Ethernet Adapter #2 : length null
Microsoft ISATAP Adapter #3 : length 8
WAN Miniport (IP)-WFP Native MAC Layer LightWeight Filter-0000 : length null
WAN Miniport (IP)-QoS Packet Scheduler-0000 : length null
WAN Miniport (IPv6)-WFP Native MAC Layer LightWeight Filter-0000 : length null
WAN Miniport (IPv6)-QoS Packet Scheduler-0000 : length null
WAN Miniport (Network Monitor)-WFP Native MAC Layer LightWeight Filter-0000 : length null
WAN Miniport (Network Monitor)-QoS Packet Scheduler-0000 : length null
Oracle VM Virtual Ethernet Adapter-WFP Native MAC Layer LightWeight Filter-0000 : length null
Oracle VM Virtual Ethernet Adapter-QoS Packet Scheduler-0000 : length null
Oracle VM Virtual Ethernet Adapter-WFP 802.3 MAC Layer LightWeight Filter-0000 : length null

$ java -Djava.net.preferIPv4Stack=true ListHardwareAddresses

Software Loopback Interface 1 : length null
WAN Miniport (L2TP) : length null
WAN Miniport (SSTP) : length null
WAN Miniport (IKEv2) : length null
WAN Miniport (PPTP) : length null
WAN Miniport (PPPOE) : length null
WAN Miniport (IP) : length 0
WAN Miniport (IPv6) : length 0
WAN Miniport (Network Monitor) : length 0
Microsoft Kernel Debug Network Adapter : length 0
RAS Async Adapter : length null
Oracle VM Virtual Ethernet Adapter : length 6
Oracle VM Virtual Ethernet Adapter #2 : length 6
Microsoft ISATAP Adapter #3 : length null
WAN Miniport (IP)-WFP Native MAC Layer LightWeight Filter-0000 : length 0
WAN Miniport (IP)-QoS Packet Scheduler-0000 : length 0
WAN Miniport (IPv6)-WFP Native MAC Layer LightWeight Filter-0000 : length 0
WAN Miniport (IPv6)-QoS Packet Scheduler-0000 : length 0
WAN Miniport (Network Monitor)-WFP Native MAC Layer LightWeight Filter-0000 : length 0
WAN Miniport (Network Monitor)-QoS Packet Scheduler-0000 : length 0
Oracle VM Virtual Ethernet Adapter-WFP Native MAC Layer LightWeight Filter-0000 : length 6
Oracle VM Virtual Ethernet Adapter-QoS Packet Scheduler-0000 : length 6
Oracle VM Virtual Ethernet Adapter-WFP 802.3 MAC Layer LightWeight Filter-0000 : length 6