>I'd love to see an example of such an accepted accountability at least once in my life.
I think that's the point, you wouldn't see it. If a good manager gets unreasonably or unfairly reamed by his boss, he's probably not gonna tell his team about it, because it would be a blow to morale. If it was indeed the team's dysfunction, he'd try to improve it.
When I "decided to move on", that included deciding that management was likely not in the cards for me again. Companies that have IC staff+ roles are what attract me now.
I've seen it before. After that manager stepped in to help me, I would've stepped in front of a bus for him. That is the one time I had a manager like that in my entire career.
If you need your job to live, and taking accountability means any non-zero probability of losing your job, would you take accountability? Of course it is easy to answer an hypothetical.
Sounds performative rather than anything real at stake. Managers are expected to lay down rhetoric about accountability and contextualizing their team's failure.