So yes.. As I spoke with an friend of mine who keeps forstenii he said the same like you.. But he said that you can't keeps females together but if it works with your animals than it is maybe different from animal to animal...Can't speak for elongata, but when I got my group of forstenii I was warned against housing them together. I've managed to keep two females together without issue, but males will violently ram each other, and males and females attempt to mate which can be pretty aggressive. I wouldn't advise housing a male and female together full time, and I've heard the same from more experienced keepers. You can get lucky and maybe keep two females together, though.
As Juli said, I've seen a lot of people housing elongated's together, and I assume they don't have as much of an issue…?