If I understand the question correctly, I think they're asking if they could, say, book a FP+ for 10:00 AM. Instead of going directly into the FP+ queue, they enter the standby queue, grab a pager, exit, enter the FP+ queue (still during their window) and ride, then return to the standby queue with their pager to presumably ride a second time. Using their FP+ to kill some of the standby wait time.
I'm not sure if it would work, or if the standby area allows exit and re-entry but I think that was the question being asked?