Some origins can contain different applications with different levels of security requirements. In those cases, it can be beneficial to prevent scripts running in one application from being able to open and script pages of another same-origin application. In such cases, it can be beneficial for a document to ensure its opener cannot script it, even if the opener document is a same-origin one. The `noopener-allow-popups` Cross-Origin-Opener-Policy value will allow documents to define that.
Some origins can contain different applications with different levels of security requirements. In those cases, it can be beneficial to prevent scripts running in one application from being able to open and script pages of another same-origin application. In such cases, it can be beneficial for a document to ensure its opener cannot script it, even if the opener document is a same-origin one.
Explainers: https://gist.github.com/yoavweiss/c7b61e97e6f8d207be619f87ab96ead5