I might be wrong but I think that those
standardized tests are somewhat person-adapted. This might sound off-topic, but when I took TOEFL in US couple of months ago, I found it extremely difficult. I'm in US for 4 years now, before that I worked for one of UN agencies where all communication was in English, my husband is American and he is told to correct me every time I make a mistake. I mean, I think I know English very well, but I found TOEFL extremely complex. I scored high (96%), but I have no idea how some 17-18-year-old high-school kid from lets say China or Europe can do well on it. Therefore, I think before "spitting" out the test computer takes a quick look whether you are applying for a grad or undergrad, or are you in US, UK or elsewhere. So I think GMAT also takes a peak at your info. Once again, I might be wrong, but my experience with TOEFL makes me think that standardized exams might slightly differ depending on the takers background and location.