I provided you with the "New Calvinist" statement which consciously distinguishes its aims from Old Calvinists. One of the things it finds disagreeable about Old Calvinism is "separation." For you to ask where they "fail to separate" is irrelevant. By their own confession, they aim not to separate. Either you agree with that distinctive or you don't. You indicated that you agree with it, but now your question supposes that not separating might be considered a failure.