[car] michiel: Me neither. It goes against the first rule of ARIA use:
https://www.w3.org/TR/aria-in-html/#rule1. So I think role="button" should only be used in the button section:
http://w3c.github.io/aria-practices/#button and all other examples should use a <button>. Sample code from the APG gets copied & pasted verbatim, so it should be the code we really want people to use.
I also think the button section needs a note, similar to the one in the link section:
http://w3c.github.io/aria-practices/#link, that "strongly encourages" authors to use native host language element, i.e. <button>.