The goal, afaik, is to stop facial detection software from learning to recognize you and put a face to a name, not to frustrate visual similarity searches. The images are supposed to be visually similar -- so similar that they're indistinguishable to a human viewer.
Surveillance software that purports to accurately identify a person across multiple images is not just looking for the same content with some visually insignificant modifications. It's reading your facial structure, attaching your name to it, and searching for it in every image received. Fawkes is working to defeat that specific use case, not all fuzzy matchers in general.
P.S. If you have a human assailant running a reverse image search for photos of you, I think you're well past the point that something like this could be expected to help.