If you look into the repo history you can see what it was doing before:
https://github.com/mozilla/addon-wr/blob/21ff53d2d5baab591d2...
In any case, the claim that "no user data was collected or shared" is suspect.
Users who enabled the extension and visited NBC Universal's site (and others) were sending extra HTTP header data to the server, data that identified them as a Firefox user, of a specific version, who had a particular extension installed -- that's how the "engagement" worked.
Do you think the server(s) that handled these types of "special" requests were configured to specifically _not_ log the incoming traffic or extra headers?
Do you think that NBC Universal would spend the resources to build an elaborate[1] ARG focused on digital "engagement" with fans, form a relationship with Mozilla to promote the show and ARG to Firefox users, but also specifically _not_ collect data about those users?
It seems unlikely.
[1] https://wiki.gamedetectives.net/index.php?title=Mr._Robot_AR...
Outrage is really hard to dial back, even in the face of new information - I know it is for me. I guess that's an interesting corollary for many of the events we see happening in these polarised times.