Well I think there is a separate question of "does this work on a population level" versus "does this work for any given individual". I think we are used to "vaccine mostly works for everyone" type thinking. However, I think that there are many things that will work for individuals but not for general populations.

So SATs are not generally trainable by a universal approach -- including personal tuition. I think that is believable. However, that for any given individual there is no intervention which will substantially improve their SAT results is a much stronger statement which I find less believable.