Import data limited to FDF files

In Acrobat Pro DC, I am trying to import data to populate form fields.

Why does the import form data function only accept FDF files? (all other file types are greyed-out)

My understanding was it should be able to accept both FDL and XML.

The help file: Collecting and managing PDF form data, Adobe Acrobat does mention that "Some formats are available only for specific types of PDF forms, depending on the application used to create the form".  Are there any settings I may have incorrect?

Thank you