It’s definitely related to the country of origin. I’m from Lebanon, and this is why I was given the DS-5535. No other reason.
I think they haven’t even bothered checking my background, because if they did I’m 99% sure I would have got the visa: Well educated, Very high paying career, multinational (US) company for around 10 years, visited the US a lot of times (max stay is only 10 days).
I’m also Christian, which they can obviously see on my birth certificate. Not saying that religion should be a deciding factor but that special clearance was created to mainly target muslim/middle eastern countries after 9/11.
So based on all of this info, I can confirm that country of origin is the deciding factor for DS-5535.