Today I was flying out of SEA and at the check point I was at it appeared that all of the Backscatter machines were in use so it didn’t matter what line I chose.
I also noticed that instead of the TSOs directing people whether to use the Backscatter or the metal detector, people just self-queued in front of the AIT. Instead of queuing, I just approached the metal detector and I was motioned right through. No one questioned why I wasn’t queuing for the AIT. No one made me wait for a pat down. People were just choosing the line the person before them went through.