Whether a work is transformative or not isn't the only factor that goes towards a fair use ruling. Bring transformative is just a part of the "purpose and character of use", which is a single factor weighed alongside the nature of the original work, the amount and substance used (if the "heart of the work" was copied), and the effect the derivative has on the market for the original work. It's much more complicated here, and will have to be ruled on a case-by-case basis, as far as I know, and copyright holders could potentially make many cases using the other factors that a use isn't fair. I do think it should be considered fair use, but as the law currently stands, it does appear to be more complex, at least from my point of view.

Note: I am absolutely not a legal expert.