When would a policy apply if the policy is set under Defend > Vulnerability >...

In Prisma Cloud, policies set under "Defend > Vulnerability > Images > Deployed" are specifically designed to apply at runtime, i.e., when a container is instantiated from an image. This ensures that any image, regardless of its point of origin or creation time, is evaluated against the defined vulnerability policies at the time it is deployed as a container in the environment. This runtime enforcement is crucial for catching vulnerabilities that may not have been present or detected during the image build phase, providing an additional layer of security for running applications​​.

https://docs.paloaltonetworks.com/prisma/prisma-cloud/22-12/prisma-cloud-compute-edition-admin/vulnerability_management/vuln_management_rules