According to the download description of the latest BIOS update:
I do not see any indication that Dell shipped the 2013 XPS 12-9Q33 with Linux. The 2013 XPS 12-9Q33 shipped with Windows 8/8.1 and we later provided Windows 10 driver support.
In any case, Dell would only support the creation of a MS-DOS bootable key, not freedos.
The "File Format" and "Format Description" are incorrect in mentioning DOS.
Regarding FreeDOS vs MS-DOS. Dell has been shipping devices with FreeDOS for years when MS-DOS was already obsoleted, and has supported FreeDOS as an environment for starting BIOS updates on several dozen of different models, so "Dell would only support the creation of a MS-DOS bootable key, not FreeDOS." is and wrong.
Doing BIOS updates from outside Windows was possible when the device shipped, so I consider this an advertised feature.
One reason to choose Dell systems in the past was good Linux support, apparently I was wrong. Providing BIOS updates not tied to Windows is likely just a single build time switch, denial by Dell to do so is unacceptable.
Actually, it states,
Creating a USB Bootable Storage Device Using FreeDOS (Legacy Systems)
"This process is provided as a courtesy, and requires the use of third party utilities to create the bootable USB key. This process will not be supported by Dell Technical Support. Please proceed at your own risk."
and directs you to a non-Dell 3rd party site =
The FreeDOS Base ISO 1.0, located at www.freedos.org/download External Link