What does en4/en5 do in macOS Big Sur running on a new M1 Mac mini?

Question

When I reinstall macOS Big Sur (11.2.3) on my new M1 Mac mini, I found that there are 2 more network interfaces，they are Ethernet Adaptor (en4) and Ethernet Adaptor (en5).

{
    Active = 1;
    "BSD Name" = en4;
    HiddenConfiguration = 1;
    IOBuiltin = 0;
    IOInterfaceNamePrefix = en;
    IOInterfaceType = 6;
    IOInterfaceUnit = 4;
    IOMACAddress = {length = 6, bytes = 0x1e10f21a3e44};
    IOPathMatch = "IOService:/AppleARMPE/arm-io@10F00000/AppleT810xIO/usb-drd0@82280000/AppleT8103USBXDCI@0/AppleUSBNCMData@1/AppleUSBDeviceNCMData/en4";
    SCNetworkInterfaceInfo =             {
        UserDefinedName = "Ethernet Adaptor (en4)";
    };
    SCNetworkInterfaceType = Ethernet;
}

I can disable them using the networkstep command:

networksetup -setnetworkserviceenabled "Ethernet Adaptor (en4)" off

but I can't delete it and get an error:

networksetup -removenetworkservice "Ethernet Adaptor (en4)"
You cannot remove Ethernet Adaptor (en4) because there aren't any other network services on Ethernet Adaptor (en4). 
** Error: The parameters were not valid.

When I check the “System Report” under “About This Mac” there is no USB / Thunderbolt device connected to the Mac mini, except for the mouse, keyboard and network cable.

all network interfaces
Bluetooth PAN BSD:en6 type: Ethernet
Ethernet BSD:en0 type: Ethernet
Ethernet Adaptor (en4) BSD: en4 type: Ethernet
Ethernet Adaptor (en5) BSD: en5 type: Ethernet
Thunderbolt Bridge BSD: bridge0 type: Ethernet
Wi-Fi BSD:en1 type: AirPort

So my question is:

1. What is the purpose of these 2 network interfaces？
2. What does the error prompt when deleting really mean？
3. How to delete it?