ELL has become a funnel through which questions that some ELU users find not to be germane to their interests are gotten rid of, despite that many of such questions are well within the described parameters for ELU. It's my opinion that some members would prefer it if ELU were somewhat of an ivory tower, but others and there are many, do not feel this way. Nevertheless, it is quite easy for certain, perhaps prejudicial, members to work together and migrate posts.
But some questions clearly do not belong on ELL which is specifically set up for learners. Furthermore, questions about grammar on ELU are treated differently than those on ELL by virtue of the differences between how language instructors perceive grammar (prescirptively), and how ELU members perceive the language (in linguistics terms and descriptive grammars and to some extent what is acceptable and what is not). Instructive grammars, even for basic concepts, are notoriously inconsistent and this fact really compounds the learner's challenge. Linguistic grammar is much more consistent, particularly with regard to the basics. I strive to make any answers I provide to learners, no matter how simplified they may be, consistent with established linguistic explanations of how English actually works.
When I ask a question on ELU it is not because I lack understanding or sophistication, it is because I want a deeper understanding of the linguistic principles behind it. On ELL answers tend to be overly simple, inconsistent and from instructors and novices who do not have a very deep understanding of linguistics and they are much less helpful to me. Moreover, ELL is for learners, not for teachers, who have very different concerns from learners.