This study is hilariously titled "Studying Philosophy Does Make People Better Thinkers". The hilarity comes from the fact the study is poorly thought out. It doesn't show what it says. The authors controlled for a handful of variables and concluded philosophy study was causal.

If you control for sex, race, religion, income, father's education, mother's education, and political orientation, school FE, etc., you don't get to conclude that residual differences are treatment effects! Doing that fails because of residual confounding.

As it happens, I have a recent article on this subject: