that women and people of knowledge are coded as leaders and people of brute force as followers,

I have to strongly disagree with your friend. In the show's defense, they think they are doing this, and are honestly trying. It's full of fail, imo.

Were you aware that the creator says Stiles is bi?

No, and I have yet to find this, though I looked again when I read your comment. He talks a lot about being open to the possibility that Stiles could be bi, and he admits to hinting at it. However, in this panel he discusses it only as a possibility, and it sounds like one he hasn't committed to yet.

Stiles is so frequently coded as 'the girl.'

I realized that that had to be the case today as I went searching for fanfic. It's too bad. Though I have to say Tony Stark so often being coded as 'the girl' in Steve/Tony fanfic is even less comprehensible to me. I mean, I don't understand why anyone needs to be 'the girl,' or why being a 'girl' seems to mean to fandom what it does, but with some pairings I do find it a little more understandable than others, though no less frustrating.