The extremely powerful part imo is what it implies about the person owning the mistake and how they might change future behavior because of it. I think it's less about the effect it had on the other person, who as you point out was entitled to anger and low expectations of you. Can it (powerfully) de-escalate things relative to how these situations often play out? Yes, but if the goal of owning mistakes becomes about minimizing the consequences you face for them, it seems more meh. If it's to recognize mistakes and be accountable (particularly to yourself), it seems more powerful.

I worry a bit about the "when used correctly" part because it suggests only owning mistakes sometimes, but it could be read many ways.