Hear me out: if someone believes in horoscopes, they know what each sign mean. Which means they recognise themselves into a sign. Which means they will mostly act in ways to conform to that sign, giving you a way to figure that person out. The sign tells it all, it’s a self-fulfilling prophecy.
In my experience the big problem is not people self ascribing personality types but type casting others. When you expect others to have certain traits you also treat them accordingly.
I can’t believe she has trouble speaking in front of crowds, she’s a lion after all.
Then again horoscopes aren’t unified or anything and you can just cherry pick from different sources and cultures to believe anything.