This is working as designed in the New User Experience. In the New User Experience, persistence is used in most cases, so that the New UX remembers the last settings checked when a user created a timesheet and those are the defaults checked for the next timesheet created. The user specific Classic UI configuration settings used in Classic timesheets to set default settings in timesheets was replaced with the persistence option in the New User Experience and the Classic UI settings for a user are not supported in the New User Experience.
When a user first creates a timesheet, it will default to what was set by the Administrator in Administration->Project Management->Timesheet options (See KB000124960
for more details), but going forward, the application will use what was last selected by user when they created the previous timesheet.