I'm a bit confused how you see Mio's introduction and jump straight to "amateur author" instead of thinking that perhaps she is a deliberate mystery. Spoilers for v8 but did you not notice how Hubert seems to have never heard of her until she walks into the room, then suddenly acts like he's known her all along? Or how the memories section is amended to include scenes we've never seen before? Or the little pop up that says something like "new? character profile added". There's something going on with her, and her introduction seems clearly intended to be jarring . If you want to criticize it as a mystery, that's fine, but I think dismissing it as simply not bothering to introduce a character is frankly wrong.
Yeah it's very confusing what they are saying there. Her introduction actually reminded me a lot of a horror story I listed to a bit ago. I think it was called fleshgait. I even used the concept for a creature in D&D campaign running. So was quite entertained to see that concept being used, especially in Yuri reading of all places.