This is somewhat inaccurate from a physical perspective. What you say would be applicable to the attenuation of gamma rays, which is governed by low-probability interactions and is therefore exponential. But alpha particles, being charged an heavy, lose energy continuously through electron interactions and have a relatively fixed range in matter, beyond which the incidence is practically zero.

Shielding is not a crude term, it is indeed used as technical language in the world of radiation safety. You are also using the term attenuation incorrectly, as sibling comment points out.

Those big backscatter X-ray machines [1] have a powerful X-Ray tube. Not that I'd be worried if I flew once a month, but if I was a member of the aircrew and going through more than once a day I'd be concerned. Think about when you get a medical or dental X-Ray and the operator puts on a lead apron and goes around a corner -- they don't get anywhere near the dose that you get, but they are around the machine all the time time. TSA staff did none of that.

Those machines were killed off because it was easy to demonstrate walking right through them and not getting detected if you wear a gun in a holster the way you would normally wear a gun if you weren't trying to hide it. The trouble is it depends on the gun being between you and the scanner because the gun appears black against the white radiation bouncing back from all the hydrogen atoms in you. With no background the gun is black-on-black and invisible. When people realized you could put a cop in front of the scanner and demo that the scanner couldn't see his gun it got around quickly that the scanner was worthless. [2]

[1] https://en.wikipedia.org/wiki/Backscatter_X-ray

[2] Ok, instead of getting scanned twice on your front and back they could scan you four times but this is getting ridiculous.

I'm not sure what is the context of your link. Is it supposed to show that TSA employees are not permitted to wear dosimeters? Because if so, I can't find that in there.