I’ve never met a bi person who insisted that they’re attraction to the genders were equal. Many had preferences (mostly into women, but defintely go with certain guys) and many had phases (more into men today, but was previously crushing hard on that girl). It’s one of the commonly talked about sources of bianxiety, that you can go through a period where you start thinking “am I really bi? Maybe I’m just straight / gay” and then you see someone and remember “no, I’m totally bi”. Bi erasure is such a thing it even effects bi folks! (source am bi, have lots of bi friends)