you make the claim They are likely unsafe, and some small subset of people scanned may end up quite sick.
But there is still no evidence from what you are saying. I felt, in another variation of Poe's law, that you were in fact making a claim re backscatter for people claiming sickness after moving through one. In the same manner that people claim that they can detect wifi signals and it makes them sick, or fluoride in the water is making them sick, or just why are there rainbows in our water these days?
Quoting figures I feel is even more relevant - if you are giving someone 1/200th of a CXR, you can't claim that the CXR is only penetrating the internal organs - some fraction, perhaps 1/200th (maybe less) is going to be absorbed by the skin too, because, as you would well know, that is how X-rays work.
The fact we have greater penetration at the higher energies used for a CXR or other diagnostic imaging does not rule out using the comparison to Backscatter X-rays. In fact, it can be used to validate it.
Please note again that I am not suggesting that these machines should be rolled out everywhere and that we should have to use them, because I think it's a stupid security measure.