Some operational details of the Fill if Empty option you should be aware of.
Selected Fill if Empty checkboxes are ignored when the anonymization template is being used to generate synthetic data as part of a seeding job.
The selected option isn't applied to object fields that have a Replace with option of either Skip or Clear.
With dependent picklists - the child’s field checkbox inherits the option value of its parent’s field checkbox [selected/cleared].
The option doesn't support the following object fields. (the options checkbox is disabled):
- Multiple Picklists
- Attachments/files actual content
- Boolean