I’d have to disagree with that. We can have preferences, it’s just not an important factor. Kind of like a preference for hair or eye color. Does it really matter if someone has dark eyes and red hair (my preference)? No, I just tend to like those features better.
Omnisexuals, on the other hand, do use their preferences (if any) as a factor.
This explains it much better than I ever could: https://www.quora.com/Can-a-pansexual-have-a-preference-in-gender