Just grasping at things, is it for virtual NIC setups, where there may be multiple device names for a single physical device, 'tun0', 'eth0.1' and so on, in the config? I don't have anything that matches on any of my routers either, but I thought it looked like a potential source of error for people with vpns or vlans on wan or LAGG or ???
In any case, it appears to be no-op code in 22.03 and later, so someone who knows what's going should give it a glance.