Inquiry About Mandatory Nature and Behavior of Planning Start Date in FBDI

Regarding the FBDI for tasks (ProjectTasksImportTemplate), the Planning Start Date (planning_start_date) is not a mandatory field in the FBDI template; however, on the UI, it is marked with an asterisk, making it appear as a required field. If this field is left blank during import, will the import process automatically populate it with the import date, or will it be set based on the project’s associated start date?