It addresses the low hanging fruit - say they didn't do this in general, and someone doing their research on bypassing any security red flags applies & gets a job in say the State Department. That person now is in a powerful position to sabotage the government. Now what if such a person was turned by a foreign government or terrorist group beforehand? This person now has the ability to wreck havoc due to insufficient screening, and the government gets criticized for not doing enough to protect national security.
You can't stop every problem, but you can minimize it as much as possible.
This is why you need layers of security. If passing a "lie detector" test gives you unfettered access to information that could potentially sabotage the government (to the point where foreign terrorists or governments would be interested in such information), then the system that secures said information needs to be changed. When you build a web application the cardinal rule is never trust the client, which should be the default assumption here, irrespective of the results of some pop-science "examination."
It's not as simple as in software development - trust has to be given that people are acting in the best interests of the country, and people have to have access to sensitive information in the government.
The only way you can secure against this is to control who you hire, and control as much as possible what they can do. To that end, sharing of this data is perfectly reasonable, as long as safeguards are in place for who uses the data, which is almost always there from my experience.
The fact that the list exists got out, so there are clearly not enough safeguards. Honest question coming. Do you subscribe to the "I have nothing to hide" notion?
I happen to have nothing to hide, and am not someone too concerned about others using data about me, but I also possess a security clearance & am a Marine reservist, so as someone involved with national security to a minor degree (I'm just a junior infantry rifleman in the Corps) & living in DC, I have some familiarity with the policies set on sensitive information & some insight into why things are done a particular way in the federal government. Civilian career-wise, I don't work for the government in any capacity & wouldn't want to (I'm a mid/senior web developer).
You can't stop every problem, but you can minimize it as much as possible.