there is certain cases where a cluster is unable to start a transition to multi arch using oc adm upgrade --to-multi-arch command, such as a disconnected cluster with no local OSUS available, or other cases where CVO is in RetrievedUpdates=False condition.
in these cases, while oc client may be expected to accept the aforementioned command, however there should be an indication such as ReleaseAccepted=False in CVO conditions providing a feedback that no transition is possible at this stage.

4.13.0-ec.2 but seen elsewhere

100%

1. a single arch cluster with RetrievedUpdates=False
2. apply the command and watch cvo status

success message returned by oc client
.spec.desiredUpdate is set accordingly
cluster is not progressing
no indication whatsoever in cvo conditions

cvo conditions should reflect the inability to transition to multi arch, such as ReleaseAccepted=False with appropriate message

in .spec
desiredUpdate:
    architecture:    Multi
    force:    false
    image:    
    version:    4.13.0-ec.2   <--whatever version cluster is currently on
in cvo History:
2023-02-28T16:09:29Z 2023-02-28T16:33:33Z Completed 4.13.0-ec.2 quay.io/openshift-release-dev/ocp-release@sha256:01192353b3c3e536779cfa0fc910064299df15ce01be0cff7188868588d32321
cvo Conditions:
2023-02-28T16:09:29Z RetrievedUpdates=False VersionNotFound: Unable to retrieve available updates: currently reconciling cluster version 4.13.0-ec.2 not found in the "stable-4.12" channel
2023-02-28T16:09:29Z ImplicitlyEnabledCapabilities=False AsExpected: Capabilities match configured spec
2023-02-28T16:09:29Z ReleaseAccepted=True PayloadLoaded: Payload loaded version="4.13.0-ec.2" image="quay.io/openshift-release-dev/ocp-release@sha256:01192353b3c3e536779cfa0fc910064299df15ce01be0cff7188868588d32321" architecture="amd64"
2023-02-28T16:33:33Z Available=True : Done applying 4.13.0-ec.2
2023-02-28T16:33:33Z Failing=False : 
2023-02-28T16:33:33Z Progressing=False : Cluster version is 4.13.0-ec.2