It makes sense to me, they are capable of reading the story, at a skills level, but without the social and emotional intelligence to recognise that as it is a story, then copying the behaviour would not be a good thing to do. But books aimed at their age group in terms of skills level will probably be inordinately dull to them and risk put them off reading altogether.
I had a very advanced reading ability as a child, I had an adult reading age capability by about 11, and I had a huge enthusiasm for reading. I know my parents struggled to give me age appropriate books, and enough of them to stop me getting bored, or worse, helping myself to adult books that I could read, but not understand or process properly, like my dad's Stephen King collection.
I loved Dick King Smith, the worst witch, milly molly mandy, Enid Blyton, Roald Dahl etc. Also some classics, like Black Beauty, and the What Katie Did series, Run With the Wind. But I also loved non fiction too, it might be worth looking at what non fiction books might spark their interest.