The apology resolved the interpersonal situation. It hadn't resolved the neurological one.

Those are different things, and "just move on" implicitly treats them as the same.

The shame spiral after emotional flooding isn't weakness or excessive sensitivity. It's the Default Mode Network failing to deactivate after a social threat, feeding emotionally charged memories back into the threat-detection system, which responds as if the threat is still present.

The person isn't choosing to ruminate. The brain's architecture is doing it for them.

Understanding this doesn't stop the loop immediately. But it changes the relationship to it.