I believe it should be common to lock a template to avoid unintentional changes to the template. However, you are able to create a VM off the template but that VM configuration is also locked. This prevents any changes in the first screen that comes up during the process, which is to specify the name of the VM. You will have to complete the VM creation process with the default name (no explanation in the UI why nothing is editable). Once the VM is created, you would then need to unlock the VM before making any changes.
Please consider not locking the VM by default.
Please consider not locking the VM by default.