Leapforce's exam is not hard to pass at all. At least it wasn't when I worked for them back in 2010 as an 18 year old with English as a second language.
The reason that the people that one rater's referred didn't pass might simply be a cultural difference between the rater's locale and the locale of whoever designed the "right" answers.
For example, if you assume the test was written by people in SV it would not be a stretch to imagine a bunch of people failing because they (for example) failed to flag content that included the confederate battle flag as offensive.