Automation: Set due-date in subitem based on primary item due date

I have an automation set up to create multiple subitems based on the type of project being added.

Each subitem should have the same due date as the project itself. Currently, there doesn’t seem to be a way to set the due date to anything except a fixed date that is always the same date regardless of when the automation runs (which seems like a bug).

I was fine just leaving the subitem date field blank, but if you do that, the reporting tool on team member capacity no longer works, as it’s looking for due dates.