Overlapping of SAs when it is manually assigned on the same timeslot & resource where SAs are already scheduled by optimisation

n Salesforce Field Service (SFS), when the optimization engine (such as the scheduling optimizer) automatically schedules Service Appointments (SAs), and a dispatcher then manually assigns a new Service Appointment to the same time slot and resource, the system does not automatically resolve the resulting overlap.
This behavior occurs when Enhanced Scheduling and Optimization (ESO) is not enabled. Even if the Scheduling Policy has the "Fix Overlap" option enabled, this setting alone does not prevent overlaps during manual assignments. The "Fix Overlap" setting must also be explicitly enabled in Salesforce Field Service Settings to take effect.

Below is the screenshot of the Field Service Settings page showing the Dynamic Gantt section with the Fix Overlap checkbox unchecked, illustrating the configuration state that allows overlapping Service Appointments.]