applying oc adm upgrade --to-multi-arch on a cluster which is already multi-arch returns:
Requested update to multi cluster architecture
and resets .spec.desiredUpdate to
desiredUpdate:
    architecture:    Multi
    force:    false
    image:    
    version:    4.13.0-ec.2   <--whatever version cluster is currently on
needlessly, which:
a. clears whatever was set in .spec.desiredUpdate at the moment
b. provides no indication whatsoever that the cluster is already multi and not going to progress

4.13.0-ec.2 but seen elsewhere

100%

1. install multi-arch cluster
2. apply the aforementioned command

a success message returned by the command
.spec.desiredUpgrade got overridden to aforementioned values 

at least a warning in stderr, better yet a guard like --allow-upgrade-with-warnings or such