Screening efforts aren’t obligatory. The way the TSA has their system (with precheck and in part with CBP with global entry) is that they formulate a risk factor versus traffic flow. Age, gender, etc. (all the stuff you fill out when you book your ticket) comes into play, inclusive of a frequent flyer participation, etc.. This varies by airport, but airports with more traffic are more likely to utilize random selection into TSA precheck (or limiting restrictions such as shoes) to lessen stress on the system during peak hours. I’ve certainly seen the shoes restriction lifted at JFK a lot over the years.
It’s entirely possible that they are extending the utilization of that system with more workers calling out sick-of-shutdown, which is why the shutdown is making air travel “less safe.”
