"What is the significance of this?" Nothing at all. The PC cannot respond to any form of LAN traffic unless wake on LAN is enabled in BIOS. Try switching that client off at the mains and I think you will see the router's Ethernet light go out, based on my own experience. The WAN is always active, of course, but so is the LAN while the adapters still have some power in them. It doesn't mean that there is any throughput at all.