The Due Date field does not appear in issue details when using the Export -> Printable view. This is true even though Due Date is present on both the View and Edit screens.

The Printable view, is just an html variation of the View page. Where an export that generates a file would be a service that parses and prepares data into a file.

Due Date is already defined as a field to display. As a defined field, it does indeed appear on the standard view - it's just missing from the alternate Printable view.

Steps to reproduce

1. On the issue page, navigate to Export > Printable.
2. Notice how the Due Date column is missing.