Personally I don't find it too confusing anymore, I just need a moment to get re-oriented to the statsmodels notation.  But the first time I used statsmodels endog and exog sent me on a half-hour expedition to learn what they were all about.  Most people probably would not have spent that long -- they would have either understood more quickly or they would have just moved on to something else.

After reading the discussion in https://github.com/statsmodels/statsmodels/issues/395 I can see how using endog and exog instead of y and x could help maintainability and development by putting more semantics into the variable names, especially if you are used to that system.  I think it's OK that statsmodels has a handful of developers actively contributing and testing research code using eccentric but internally consistent notation, and I assume that other projects will start repackaging the code as it matures and give it a less eccentric interface.