Personally, if someone accuses me of lying, but I am actually telling the truth, I immediately start acting like a liar. It's really embarrassing and hard to explain. I can't believe such a seasoned reporter is leaning so hard on "his face went red."
In reality, they measure a bunch of things that may indicate lying, but they are just as likely to indicate that a person is nervous or reacting to the fact they're being tested at all.
They're typically inadmissible in court these days, however, there is still a pretty solid amount of blind trust in their results.
That part of the article gives a similar "lie detecting" hypothesis, just without the machine.
Naturally, this journalist doesn't seem to care much about any of that, or that it wouldn't really change anything at this point besides making the life of whoever it actually is hell.
I grew up evangelical and I've noticed this tendency in myself, and saw the connection to how the authorities at my school or church basically demanded dishonest performances or apologies under threat of physical punishment. Several friends over the years have said roughly the same, so I have an armchair theory this is pretty prevalent for that sort of childhood.