Overlapping permits on the same equipment are a real risk because each permit can look fine on its own while the combination is dangerous, like an isolation being removed for one job while another crew is still working inside. On paper, catching that depends on the permit coordinator remembering every active permit.
A digital system can check every new permit against the active permits on the same equipment and its isolations, and flag the overlap before the permit is approved. Interface does this kind of conflict detection on the site model, so the person issuing the permit can see what else is going on at that equipment before signing off.