Not having a real name policy isn't the same as being anonymous. Back in the day my irc nick and my WoW username were far more well known than I, the human, will ever be.
I think the point is that there's a distinct disconnect between your profile on Reddit (and any other sites you share the username with) and your physical person, at least up until the point where you (ideally) make the connection public yourself if desired.
It's anonymous insofar as the "person" on reddit is not easily attributable to the physical person themselves.
There is one. It was used a couple comments up.
Pseudonymous. It's an actual word, not just made up.
My point stands, though - despite the misusage of the word anonymous there's a real difference between how facebook treats identity and how reddit does. And it massively affects how communities in both interact.
https://www.reddit.com/user/Throwaway8675309
Also no surprise, the account was active for only ~5 days.