No, that doesn't work at all. OP is saying that he draws conclusions about someone's personality based on the Meyers-Briggs type with which they identify. That logic doesn't apply to the zodiac because your star-sign is based on your birthday. People don't lie about their birthday to become a Virgo. But they might fudge the answers to the Meyers-Briggs survey so they appear more "introverted" and "thinking". If you compare someone's self-view ("I'm an introvert!") with their behavior (definitely an extrovert), you can draw conclusions. This is more than "fun to talk about". It's standard practice in psychology.