While some of these were available on previous releases, this is to ensure a more complete and consistent (Jira and Confluence) set of variables and include reference support.
chosen instead of userFullName as display name is now more current Atlassian terminology especially on Cloud
These will be set on addUser and getUser. And available on the runFromUser action.
When the reference parameter is used on addUser and getUser, the variable will be defined with value of userKey so it represents a unique identifier for other actions needing a user on both Cloud and Server platforms.