If a workshop has "submissions deadline" enabled, the timeline block on student's dashboard will tag the activity with 'Overdue' on the submission step even if the student has submitted his/her work before the deadline. 

The "overdue" tag is displayed :

• if workshop submissions deadline is set and enabled
• if workshop submissions deadline is over
• even if work has been submitted before submissions deadline

whereas it should only be tagged as overdue, if no work has been submitted before deadline or if work has been submitted after deadline and if it has been allowed by teacher.