Multiselect Attribute + Default Values + Attribute Dependency

Hello! I've created a form that includes a dependency between a dropdown custom attribute (parent) and a multiselect custom attribute (child). When the multiselect become visible (per the parent), I would like all of its options to be selected by default. The dependency is functioning as expected, but the default selections are not. When I select all and save the form (Default Applied ✓) the options are not selected when I preview the form (I have previewed the form in the form designer and the service catalog). If I remove the dependency, though, the default selections work and all options are selected. Is this expected functionality or am I missing a step? 

I recently did a similar things between two other custom attributes: radio select (parent) and checklist (child), and it was successful. When the checklist became visible (per the parent), all options were selected (per my configurations in the form designer).

Thank you!