Sorry, I don't see where they are generating random noise or keywords from your link. The link seems to be discussing the merits of a relay of existing traffic.
Relaying 'existing' traffic is the "random noise". It provides obscure, 'random' traffic between nodes but serves a purpose by providing bandwidth.
The content of this traffic could easily be a useless packet, IRC, HTTP, etc.
https://trac.torproject.org/projects/tor/wiki/doc/TorFAQ#DoI...
I2P does similar in making every user an internal participant. A network wholly dedicated to pushing redundant/null traffic is not a thing, AFAIK.
Tor, I2P and other networks I'm sure, methods of doing things are more "useful" by providing bandwidth whilst also giving cover traffic.