Both the manager and the friend-of-friend could be correct – it depends on the team. Some teams encourage (but don't require) a group feedback session where everything is out in the open; others encourage private feedback.
But either way, the goal is the same – not to target you or make you feel inadequate, but for you to discover things that you might not have realized were negatively impacting the team.
Group feedback meetings do exist, but I can't imagine that anyone would be penalized (even in thought) for choosing not to participate.
The way I see it, people will talk about their coworkers at any workplace. At most places it's behind their back; here we have respect enough for one another to give each other constructive feedback directly instead of gossiping. It makes a lot of sense to me, but I guess not everybody feels that way. If your manager doesn't make it clear that group feedback is optional, that would be a great piece of feedback for your manager!
So I think "criticized in public as a matter of course" is a mischaracterization. IME managers go to great lengths to ensure that people are treated respectfully and not made to feel pressured to participate in things they aren't comfortable with. And "fired one day unexpectedly" is certainly not the norm – I'm not aware of anyone who was let go without having been told weeks or months in advance about issues they needed to address. That's not to say it couldn't happen, because it could happen at any workplace. But it's not the norm.
Edit: Should also mention that the feedback cycle also includes positive feedback. It's not just a gripe fest. You identify things that your colleague is doing well/things you appreciate, and also things that they could improve.