Select 'Copy time entries from previous timesheet' on the Timesheet Options page, on a new timesheet click 'Populate'. Tasks added into the new timesheet include not only the ones from the previous timesheet, but also ones that the resource is currently assigned to, open for time entry, and have non-zero ETC. Is this a defect?
This is per the current design. Reference the following article for more information.
KB000027000: Clarity Timesheet Population (What determines tasks appearing on a timesheet)
There is an open Community Idea that is currently under review by our Product Management team.
Community Idea: Populate Button on Timesheet - Change behavior to Copy Time Entries from previous Timesheet