[ApK]

I don't know about the 5 year claim (I mean, I guess you could only use the router once in 5 years....) or any broad assurance of scope, but it is certainly true that routing tables are not the same as logs, and a forensic analysis of even a cheap consumer router will reveal data that the router MUST have internally in order to function, regardless of logging, including info about NAT/PAT mappings and which internal private IP got or sent which request from which external IP.

It's even possible (though I don't recall the protocol specifics---"loose-source routing" perhaps?) that your private IP is included along with the packet data and may be logged by other systems on the Internet.