It can help a lot, since isolation planning today usually means someone tracing lines on printed P&IDs with a highlighter to find every valve and blind needed to isolate a piece of equipment. A digital twin built from the P&IDs already knows how equipment and lines connect, so it can suggest the isolation boundary and the points needed to achieve it.
The suggestion is a starting point for the isolation planner, not a finished isolation, since drawings are not always accurate and some isolations depend on site practice that is not on the drawing. It saves the planner the tracing work and leaves them to focus on checking and approving the plan.