Dang, that's been a thing for almost two years? I definitely didn't hear anything about it.
Hopefully they do finally roll it out to existing accounts but at this point I don't even trust them. A third breach is not unlikely at all IMO and people will just scoop those answers up, maybe even stuffing them into recovery fields for other sites too (if you're using the same answers, so don't do that).
Basically, I can't trust TNT not to somehow screw us over in some spectacular new fashion every time they try something new. I hope this is taken further and actually helps, for the good of the greater Neopets community and our collective sanity. I'm glad they're at least doing it on the new accounts. Just wish we had access to this recovery option before everything went upside down.