Shelf is a parameter on the add review method but not the update review method. If I want to update a book from currently-reading to read and update a rating or review text, it takes two API calls but the initial review creation only took one.
Actually, it would be handy if there was just one Add Review method with review ID as an optional parameter. If it's not provided, create the review. If it is, it's a review update.
Understand the request and it makes sense, though since the API does support all the functions you need to perform, I think it's unlikely we'll make that change soon. If lots of community support for this builds, we can take it under consideration.
Actually, it would be handy if there was just one Add Review method with review ID as an optional parameter. If it's not provided, create the review. If it is, it's a review update.