If the disk from one VM is attached to another VM using use existing PVC and when the source VM is deleted, the disk from other VM will also be deleted. 

OCP 4.16

Always

1. I create a Linux VM using a template that takes the boot source disk from Registry.
2. I create a new disk (PVC is created) to the VM (make it persistent).
3. Mount to it in the VM and read and write to it.
4. Create a new  Linux VM from the same template
5. Attach the new disk from the old VM to the new one VM and make it persistent.
6. Mount to it in the new VM and read and write to it.
7. Delete the old VM .
8. The disk from new VM is also delete and rebooting vm will lose the disk. 

Disk deleted when attached to two vms

Disk should not be deleted or give warning that it is attached to another VM or something like that.