While I'm not familiar with the geography of ORD's T3, I do believe you are referring to the First/EXP/PLT security line, where the current PreCheck setup is. The F/EXP/PLT line is way over to the left (when facing the checkpoint) of the PriorityAAccess line and all the other AA desks and security checkpoints. I've often seen the PA line to be very long, but never the F/EXP/PLT line, and PreCheck is filtered out by the initial scanner and directed to the left side of the ID checkers. Never had much of any wait for PreCheck.