It’s a polite way of saying that you’ll be randomly interrogated.

It’s like the FAANG interview process. Everyone knows it’s suboptimal, but nobody knows how to do better at that scale.

Close.

It's similar because there are lots of false negatives, but few false positives.

My understanding is that it's used as an "interrogation" technique and that they don't really care what the machine tells them.

They do, I had a clearance rejected because the examiner was convinced I had previous involvement in drug manufacturing. I don’t. I’ve never even used them. Hell, I barely drink. I ended up getting a much better non-clearance job offer elsewhere so it didn’t ultimately negatively affect my career, but it’s still irritating.

It’s a standard practice for a tier of Top Secret security clearance.

Is this a rhetorical question?