But I've found as I've written more stories, my characters can surprise me. I realise as I'm writing that Character Z would do this, rather than that, and then stop to think about exactly why this is. I also don't think it is possible to know everything about your character right from the start. I think the whole point of the first draft (and often the second one too) is to find out if you really do know what the story is and to discover just what your characters are made of.
I love that voyage of discovery because to date I've found that yes, my outline was right but there was more to Character Z than I initially thought and I use that discovery in my editing to deepen my character portrayals as I'm now writing about that character with more knowledge than I had at the outset. I do not think the character biography would bypass this process. It would only help me to get to describing their physical presence a bit quicker and I believe that is not the most important thing about them. I see my way of doing things here as having the bones first (the character trait) and then fleshing them out with the physical presence, their way of speaking and so on. And all I can say is it works for me.
I also think you need to put your characters into your story so they are in "action" rather than just have them on a biography (which is inevitably a static bit of writing). Only seeing them in "action" reveals what they are truly like but it is such fun finding this out and I really love this aspect of writing. Hope you do too.