Learning any subject in any domain, deeply has value, and that learning is transferable. I think when the analysis is done, saying that chess doesn’t make one smarter per se, the researchers are starting from a baseline where student a and student B are equal in all regards, and in addition to student B has learned to chess. While student a might not know chess they could have spent an equal amount of time learning something else and it’s that time learning things that’s important not necessarily the subject matter.