The difference is Socionics and Enneagram are different typology systems that were created separately and there is a lot of overlap between them. You can also choose to ignore subtype systems from both of them. Like for instance, I ignore sub wings from the Enneagram and I take DCNH from Socionics with a grain of salt.
I get your point that having more types is just breaking down the theory further, but I personally find it redundant past a certain point. This is why I don't take Objective Personality seriously because breaking down Jung's 8 functions into 512 types is redundancy even if there is some validity in it. They are more likely to make an error in several of the types like you mentioned too.
“We cannot change the cards we are dealt, just how we play the hand.” Randy Pausch
Ne-IEE
6w7 sp/sx
6w7-9w1-4w5