Is anything that is abstract, imaginary? Not in my estimation.
Having said that, MBTI does not describe much that is real. Its dichotomies and explanations are vague and subjective, so it cannot be considered science. It's really a 20-century version of astrology, with all of the magical patina removed and replaced with pseudo-science. That’s not really surprising if we remember that Jung was really into the occult and read mediaeval texts on alchemy.
Think about it. The sense that MBTI is somehow objective is tacitly believed by almost everyone on this message board. Why? Because most members are seeking some form of external validation. It’s really an attempt to be acceptable to the outside world. If it were actually descriptive, why would people constantly change their type? What does it matter to you, as an individual? Wouldn’t you take the same actions if your self-applied label was INFP or ESTJ? People confuse and blur the line between action and description with this stuff, and then behave as if the label they chose is internally meaningful.
A scientific test would be rigorous and exhaustive, because science attempts to describe the real. You as the test taker, do not get to determine the outcome, because the results must be valid when judged using the scientific method.