When there is a single resource scheduling booking for a task, and the task Assigned To, Start Date & Due Date are populated then any change to these fields on either the task or the schedule booking will update the other. The three fields that are kept in sync are Assigned To, Start Date & End Date.
However, if there are multiple bookings for the same task, or multiple users are assigned to the same task then these fields are not synced. This is because multiple bookings or multiple task assignments indicate that multiple team members are involved in work being done on the task, and their individual bookings may have different timelines. The task due date represents the deadline for the client or project deliverable, while the resource booking serves as a schedule for an individual team member to complete their part of the task.
These due dates may differ because the overall task deadline remains the same, but individual team members may have different schedules or durations for their contributions.