So my initial post is out-of-date:

This ETD screening process may require you to lift or remove some of your
clothing in order to obtain the ETD sample.

From Cookie Jarvis:

The ETD screening process may require you to lift or raise some of your clothing in order to obtain the ETD sample. (Sampling areas can be accessed by you lifting your pant leg or shirtsleeve or by raising your skirt to knee-level.)

Maybe the woman who was forced to remove her slacks had some effect on the TSA to make them change their methods.