ok?

Correlations are a theoretical question. In practice you don't need to know anything about correlations to type people in a system for the same reason you don't need to know about one system to type people in another system. It's only a question when you try to make a bigger system that includes both of them. Suffice it to say that that is far beyond what we know how to do at the moment. Socionics is mostly clearly defined at this point but say Enneagram needs a lot of work before it can be formalized.