You're suggesting that Facebook is 100% accurate in determining whether a name is real, or a pseudonym.
Imagine this: someone is on Facebook and wants to hide their identity for some reason. Best examples I can think of right now is teachers who don't want their profiles accessible to their students (because high schoolers can be little shits). Or someone trying to create a new life after domestic abuse. It makes full sense that they wouldn't want to give their full name so that they can't be found. Facebook isn't good enough in real name detection to get it right 100%. How could they?
With this sort of dump, a domestic abuser can much, much more easily find the person they abused, when that person was previously under a pseudonym.
This is just a small example. It gets much more complicated when considering how many millions of phone number:Facebook IDs were released.
