Can you easily identify ‘roles’ in BL?

I’ve read a lot of BL through my teens into adulthood (21) and I don’t feel the same way about it. I don’t agree with typecasting and fetishising queer people, and the lens of ‘seme’ and ‘uke’ is not an appropriate cultural lens to look at anybody with. But. What bothers me is that whenever I look at a BL cover or read just the first chapter, I’m 99% of times right about who’ll be the top or bottom in the story.
I’m sure it’s the same with a lot of BL readers,
My question is — how??
Like they could all look different in their physique, art style yada yada but we’ll always know?? So there’s conditioning at play, of course, because we’ve been consuming formulaic archetypal narratives continually over years of developments in this genre but — I want to know your experiences too?? Because I feel really awkward about it, and it’s also just a question unanswered for me.