I just reviewed this answer. After suggesting minor improvements, my curiosity got the better of me and I checked the profile of the poster and discovered they have been a (granted mostly inactive) member for over 5 years! Is the queue misnamed? Should it be the Late Answer Low Rep queue?
I think the "new" refers to rep, and has nothing to do with how long a user has been a member. I don't know how the actual algorithm works, but I assume it's something along the lines of
if rep < N && isAnswerToOldQuestion; then.... Or, perhaps,
if numberOfAnswers < N; then ....
So I wouldn't be surprised to find answers by users who've been here for years appear in the queue. Not if they haven't answered much before.
I signed up here over two years ago and at the time made a few posts but knew very little of how the AU interface worked or what the "UbuntuQuette" was in AU.
It wasn't until four months ago (after I bricked Windows 7) that I reinstalled Ubuntu and came back to AU. Through the process of resolving 14.04 laptop upgrade to 16.04 glitches I got very keen on learning new things and started answering questions.
So yes, I would say a "new user" has nothing to do with sign-up date but more so on rep points and more specifically learning the etiquette of properly formatted Questions, Answers and Comments.