It’s more of a reminder of why DDoSes work: if you bombard the network port on a router with lots of redundant packets, you force the router to do purposeless extra work.
The extra work steals some of the router’s performance away from legitimate users, and thus legitimate traffic gets held up in the snarl.
Unfortunately, if you pick your time-wasting packets carefully, you may be able to find some router models that do even more extra work than you might expect in order to dispose of your malicious traffic.
At that point, you can cause additional harm to those routers, simply by picking the content that makes them work hardest.
BlackNurse’s “extra harm” traffic turns out to be a special sort of network packet known as an ICMP reply, short for Internet Control Message Protocol.