When creating a new VM using an instance type and customizing the VM to include an additional disk, the additional disk is set as the boot device which makes the VM unbootable.

OpenShift 4.19.16
OpenShift Virtualization 4.19.12

When creating a VM from an instance type and adding an additional disk.

1. Create VM from instance type
2. Click the Customize VM icon, select Configuration, Storage
3. Click the add disks, empty disk, just accept the defaults and click save.  Note the checkbox for the "Use this disk as boot source" checkbox is NOT selected.
4. Click Create VirtualMachine

The extra disk is marked in the YAML as the boot device instead of the rootdisk.

The rootdisk should be marked in the YAML as the boot device and the VM should boot.

When using a template and customizing the VM to add the second disk, the issue does not occur.  It only happens when using "from instance type".

Attachments - moccasin-mastodon-10.yaml is from the VM created from instance type and the salmom-leopon-10.yaml is from the VM created from a template.