I am surprised that Apple was doing it without asking for permission. I would happily allow Apple engineers to listen to failed interactions if I had a chance to pick and choose which ones to give them access to.
Users likely didn't know about it because, like most people, they didn't read the full TOS. Apple would've been smart to include a conspicuous statement about employees/contractors listening to recordings (if only to preempt this kind of PR debacle)... in addition to the legalese.