Firefox Studies aren't new, and aren't opt-out by default. They're opt-in per study, in fact. The code to run them comes with Firefox, that's it. All this HN link is is someone asking what the add-on is, not proclaiming it did anything.
It's nonetheless not obvious to me why you were downvoted; I don't know if someone else was annoyed at your definition of "new" or whether there were other dubious claims in your comment. Perhaps privacy advocates are just too exhausted and cranky to explain themselves again.