We are unable to fetch subtasks in nextgen projects for active sprints.
Example:
project="PROJECT" AND issuetype in (subTaskIssueTypes()) gives the issues and displays the sprint as well.
Whereas the below query does not return any issues. But there are subtasks in open sprints, and these are displayed in Active Sprints board.
project="PROJECT" AND issuetype in (subTaskIssueTypes()) and Sprint in openSprints().
Subtasks are not shown when we add Sprint in JQL