The Editor Tracking fields ('created_date' and 'last_edited_date' ) are available for sorting in the GeoForm application despite not being selected as 'Display field' while configuring the application.
Last Published: September 30, 2016ArcGIS Online
Bug ID Number
September 28, 2015
June 11, 2020
Operating System Version
7.0 64 Bit
Will Not Be Addressed
The development team has considered the issue or request and concluded it will not be addressed. The issue's Additional Information section may contain further explanation.
This is by design. So a user can sort by the latest edited or submitted data.