Non-cognitivism strictly speaking doesn’t imply the orthogonality thesis. For instance, one could consistently hold that increased intelligence leads to a convergence of the relevant non-cognitive attitudes. Admittedly, such a position appears implausible, which might explain the fact (if it is a fact) that non-cognitivists are more prone to accept the orthogonality thesis.
Non-cognitivism strictly speaking doesn’t imply the orthogonality thesis. For instance, one could consistently hold that increased intelligence leads to a convergence of the relevant non-cognitive attitudes. Admittedly, such a position appears implausible, which might explain the fact (if it is a fact) that non-cognitivists are more prone to accept the orthogonality thesis.