https://github.com/openshift/enhancements/pull/1690 for OTA-962 contains a test plan which can be used to verify OTA-960.

As a CVO engineer, I would like to have the test plan automated
so that we can reduce the effort of verification
while other cluster operators take the actions from the proposal.

The test plan is to verify that a new cross-arch compute instance can become a node of the cluster right after the migration to multi-arch is complete.

• Install a single-arch cluster (ClusterVersion status.conditions having Progressing=False and status.history claiming Completed).
• Migrate the cluster to a multi-arch (ClusterVersion status.conditions having Progressing=True)
• Ensure that update completes (ClusterVersion status.conditions having Progressing=False and status.history claiming Completed).
• Immediately after ClusterVersion claims completeness of the migration, create a machine set for a secondary architecture compute instances and ensure that the machine there successfully joins the cluster as a Node, within some reasonable time threshold (15m?).
   

Acceptance:

• A periodic exists for the OpenShift org that automates the above test plan.

For grooming:

• The owner of the test plan and the underlying workflow: ota or #forum-ocp-multi-arch-ci ? Slack conversation with the team.