It’s been a long time since the Oak Ridge mouse (and other mammal) experiments. I agree with your concerns.
The BIER reports are based on old data, but they do seem to converge on 1% “excess cancers” above noise for every 10 REM whole-body exposure.
We will NEVER have the data, except by syndromic monitoring. We expose lots of people to the soft xray from CRT’s, for instance, and hope that nothing statistically significant comes up.
My original point, put in energy terms, reads like this: you get exposure to more energy on the actual flight than you get from the scanner, by a factor of hundreds to one.
The scanner dose, or energy, is less than or equal to natural background in most places (20 uR here according to a Ludlum scintillator).
That all shows you have knowledge and the understanding to use it wisely. It may be that the amounts of radiation are not problematic. But this is no way to rush to make the whole population the test set.
For example, the “skin scan” with either the backscatter x-ray or the terahertz may induce some condition in the skin or the whole body response that makes it more susceptible to the cosmic radiation in high flying jets. We do not know.
And how much tuning and adjustment or calibration sensitivity is there on these machines? I’m familiar with dental office x-ray machines, and there is a still a huge variance in dosage between the the dose you’ll cat in one office with a piss-poor maintained old machine, and a another with a state-of-the-art extremely low dose digital machine.