Our hypothetical AI won't make any decisions. It just makes sketches as described and approved by witnesses. The relevant racism here is the one any witnesses may have, that's true even with a human police sketch artist.
"as described" according to what? There is simply no way to create image from words without something closely resembling decisions. Maybe "it" won't "make" those decisions, but they will be made somewhere.
Yea, somebody will have to evaluate whether the image matches the word, and that is currently done by the witnesses themselves. How is it worse than the current state?