Can't sell fast track if there's no queue!
And by the time you've got a tech down (because of ^) to add/remove a train, the queue will have changed, so they'd be chasing their tail all day adding and removing trains to match the queue
This? . I was at AT on Saturday and the queue times on the app were exaggerated by at least 20 minutes all day. Some of this can be attributed to the difficulties in estimating queues with social distancing however the fact that there were selling fast track had to have an impact the times shown.