Recently, GitHub introduced a new state for issues, namely "Not Planned" . The support for this has been added to Prow (tracking issue  and the PRs implementing it  are attached below)!
As you might be aware, issues and PRs that have been inactive for 90 or more days are auto-closed by the ci-k8s-triage-robot. When issues are auto-closed, they are closed as "Completed" which can be misleading. Which is why going forward, issues will be auto-closed as "Not Planned"  using the above mentioned support added to prow.
Please note that there is no change to the way PRs are auto-closed.
Thank you and have a great rest of the week!