I just had an early flight through Sea-Tac and asked one of the airport people if there was a priority access lane (there were a lot of people in the cattle chute). He pointed to the far end and sure enough, there was a completely empty lane that first went by a Pre-Check guy, then brought you right to the ID checker merge point of the regular lanes, but then shunted off to a different lane again. Added bonus, they were using the porno scanners on the regular lane but the Special People lane was just the old metal detectors.

Forgot to add - no one asked to see any verification of my priority access eligibility.