And borderline statements have elements of both factual and opinion statements – they can be based in objective evidence, but claims are vague enough that they can neither be unambiguously proved nor disproved by factual evidence, in part because such evidence is often conflicting, incomplete, contested or involves making predictions.
Im not sure how I feel about the use of borderline statements. I feel like they may have further confused the survey taker because of the ambiguity in the borderline statements. I am also not certain that the use of borderline statements led to any significant discovery. I suppose that they may have worked as a control, so that they might be able to more distinctively understand how a person chooses fact or opinion, but this is not made super clear in the findings.