When an application is chosen in the "Application Picker", the "Default" UpdateSet of the scoped application is not selected/created. It always selects an UpdateSet in the "global" scope.
Release or Environment
The sys_user_preference table has records with name starting with "updateSetForScope<sys_id_of_scoped_app>". The "User" and "Value" field plays a role in determining which UpdateSet will be selected in the "Update Set Picker".
1) Find the sys_id of the scoped application being selected in "Application Picker".
2) Check sys_user_preference table with name starting with "UpdateSetForScope<sys_id_of_scoped_app>"
3) In that list, in the "User" field, check if there is a record with the logged in user. If not, the "Value" column of the "(empty)" User will be used to select the UpdateSet. If "User" exists, then that "Value" sys_id will be used to select the UpdateSet. For example, in the attached picture, the 3 row from the top "Abel Tuter" is the "User". If "Abel Tuter" selects scoped app with sys_id 82878663ff123100158bffffffffff67 then UpdateSet with sys_id e14586eddbed37009895ef728a9619dd will be selected in the UpdateSet.