I'd believe this about as much as I believe palm reading or horoscopes. Seriously? Rooted in brain matter? How exactly does a whorl halfway between the eyes and the nostrils get rooted in brain matter?
Zierra has one whorl right between her eyes, quite symmetrical. In all honesty, she's about as far from an average horse as you can get. I'd be terrified to sell her because I'm pretty sure whoever she ended up with would resort to beating her from all her quirks.
Jynxy is about the same, maybe a bit higher up? She isn't interested in looking at much of anything - she's pretty average, almost a bit on the slow side at times. She processes information well, but comes across as quite disinterested in why.
As much as I'd normally agree with you smrobs, I've worked around quite a few stock horses and Jynx is especially "disinterested". She's a sweetheart and great to work with, but she's so eager to please, she almost seems to lose her own sense of self - if that makes any sense?
On the other hand, I've worked with tons of Arabs, and Zierra is extra special on the list of quirky Arabs. I'd actually rate most of my Arabs as having a very average personality - of decent intelligence and easily trained, but very laidback and uncomplicated!