From the on-topic help page:
Biology Stack Exchange is for people studying biology at any level. Questions are from students, academics and active researchers in biology and closely related fields
We tend more towards "Expert answers to your questions" (note also that this is StackExchange boilerplate, not something written specifically for this site) rather than "expert questions" - I think most of the regulars here are each the only expert here in their narrow field of interest. If I have an expert question needing a super expert answer, I go to my network of contacts rather than SE biology. Experts may ask questions here, too, but they are more likely to be outside or at the fringes of their particular expertise.
That said, we also have fairly high standards for askers. Just like SO requires askers to put in a bit of research effort and describe their problem well, SE Biology doesn't respond well to questions that are asked without any thought or prior research put in. It's useful, though not always necessary, to include references to that prior research, but often it is visible just from the quality of the question asked. We also have a strict policy against homework questions that come without effort. I think it's unethical to provide answers to questions that might prevent students from actually learning the material they study, and rude to their instructors as well.
My personal preference is that question askers not request an "ELI5" answer - the answerers can decide based on how the question is asked what level of explanation to provide.
And I'd also disagree with your characterization of your own question as one "a knowledgeable person would not ask", if we define "knowledgeable person" as someone knowledgeable about some aspect of biology. From my own perspective, though I had some general idea of what the answer would be, your question elicited an answer that gave some references and more detailed explanation than I could have. I think that's perfectly fine and valuable here.