For one thing, they're almost always made from the first two functions, ignoring the tertiary (which is quite important -- many adults have a well-developed tertiary), and they make some unwarranted assumptions about people such as that all Feelers are fluffy bunnies or all SJs are traditional and the like. Basically, they're made on basis of expected behavior, which is right for most people, but not all, since Jungian typology is based on cognitive perspectives rather than actual outwardly expressed behavior. I have a rather strong Si, for example, and have several behavioral patterns that fit strong Si use, but you yourself dismissed the idea that I could be an SJ based on the fact I'm not traditional.