I just flew from the US to Europe; at each point where I had to get my picture taken, the machine had a label on it that clearly said they would delete my data after 24 hours. (Or after use, I don't remember the precise time frame.)
Were they lying? Possibly. But this is not a matter of them trying to use weasel wording to trick you into thinking they're claiming something they're not.
You think they could be lying, but your argument is that they're being candid? Then we simply see it differently. I just read the primary source, so I know without a doubt that it's weasely.
Moreover, it was put forward as proof that they don't keep the data, but the source is actually called "Does TSA protect all data (e.g., photos) collected." What are they protecting if they don't have it? What would be the point of even doing this if they don't collect it?
But leave that aside and let's talk about your experience. Did it say the data would be deleted after 24 hours or did it say it would be deleted after use? What is use? Use could be we're operating a giant biometric database and we intend to keep doing it until the asteroid, and why wouldn't it be that?