I think there's some exaggeration as few $1 SoC parts come with 10G Ethernet, and >1G to the home is not common, but pretty much any home router can saturate its own uplink - it would be useless if it couldn't!
Also, most 1Gbit/s and faster routers have hardware-accelerated packet forwarding, aka "flow offloading", aka "hardware NAT", where forwarded packets mostly don't touch software at all.
Some routers even have internal "CPU" port of packet core with significantly slower line rate than that of external ports'. So traffic that terminates/originates at the router is necessarily quite a bit slower, regardless of possibly extra-beefy processor, and efficient software. Not really a problem since that traffic would normally be limited to UI, software updates, ARP/NDP/DHCP, and occasional first packet of a forwarded network connection.