I don't know if this was my client acting up, or perhaps an unconscious mouse movement, but I've been trying to update the application for a while now. For some reason the update button isn't working (is the server hosed? Is the internet cafe that I'm at breaking?) but when I checked the two fields you mentioned, all but one of the names were eliminated from each (and the intersection was zero).
(Edit: I was using commas instead of spaces, which might account for the weird behavior. Does YC search the usernames for each token? Because then only the last names would have had no comma, and so they they would remain)
So, I can't really remember if it was just me, but it's possibly a bug...