I've done the test a while back at school and then over the years. I always turn out (strongly in every category) INFJ although everyone pegs me as an 'intellectual' and thinker because of my math abilities and many think I'm an extrovert because I like to talk to people a lot and I like to help everyone ...
However, when you point out that the test was designed to identify decision-making, it now makes more sense to me. It's not the abilities that it's measuring but decision-making style. When dealing with people, I generally override my 'logical' assessments which I easily do but then I go ahead and decide empathically.
When I was young, I remember my mom would sometimes tell me that some schoolmate was using me (usually for some school work) and 'why did you help him' and I would answer that I knew that but that I felt he needed the help. It was always confusing to me and I still can't justify why I still do that but now I understand that the MBTI test tells me that that's what I do!
Thanks for the article.