Once you registers a IDMS/ICSP which only contains the root url for the source registry, the registry-overrides is not properly filled and they are ignored.

Sample:

apiVersion: config.openshift.io/v1
kind: ImageDigestMirrorSet
metadata:
  name: image-policy
spec:
  imageDigestMirrors:
  - mirrors:
    - registry.vshiray.net/redhat.io
    source: registry.redhat.io
  - mirrors:
    - registry.vshiray.net/connect.redhat.com
    source: registry.connect.redhat.com
  - mirrors:
    - registry.vshiray.net/gcr.io
    source: gcr.io
  - mirrors:
    - registry.vshiray.net/docker.io
    source: docker.io

    100%

    1. Deploy a IDMS with root registries
    2. Try to deploy a Disconnected HostedCluster using the internal registry
    

The registry-overrides is empty so the disconnected deployment is stuck

The registry-overrides flag is properly filled and the deployment could continue

To workaround this, you just must create a new IDMS which points to the right OCP release version:

apiVersion: config.openshift.io/v1
kind: ImageDigestMirrorSet
metadata:
  name: ocp-release
spec:
  imageDigestMirrors:
  - mirrors:
    - registry.vshiray.net/quay.io/openshift-release-dev/ocp-v4.0-art-dev
    source: quay.io/openshift-release-dev/ocp-v4.0-art-dev
  - mirrors:
    - registry.vshiray.net/quay.io/openshift-release-dev/ocp-release
    source: quay.io/openshift-release-dev/ocp-release