Enabling issues to have schedules similar, but not identical, to tasks can be done for purposes of work allocation. Unlike tasks, they cannot be assigned to multiple resources or contain constraint-based intelligent scheduling.
Issue settings can be restricted for editing to only issue managers and assignees without regard to the inherited permissions which would otherwise allow for greater permissions.
Resolution dates and estimated work field separates data fields from similar looking data in the scheduling options, but not recommended for use if scheduling is enabled to avoid confusion as to their purpose. These are simply reporting data fields with no scheduling or allocation capabilities.
Time Entry on Issues can be enabled in the Time Entry Settings by an Administrator.