About:Theme inheritance

From ZenMagick Wiki

Like in zen-cart, theme resources (template files, images, etc) that can’t be found in the current theme will be looked up in the default theme. This may be disabled by setting isEnableThemeDefaults to false.

If disabled, templates will execute a little bit faster. However, it requires to have a 'complete' theme.

Depending on the complexity of your template changes this might mean that a lot of files need to be copied without any change. One potential downside is that files may need to updated if new ZenMagick releases require modifications to those files.