@Laura2592 There must be something on your listing that only guests can see, that is invisible to everyone else, that says "Ask us the weirdest questions and make the most entitled requests you can think of". 🙂
Actually, I don't find the sheets question that odd. So many people use microfibre sheets these days, that I would be inclined to ask as well- I would hate to sleep on those. And as Kitty pointed out, most bamboo fabric is actually rayon- which is fabric that uses cellulose from trees or bamboo, or even hemp- i.e. natural fibres, but uses a chemical process to create which is, in fact, toxic to the environment.
So a serious and informed environmentalist might not even want bamboo sheets.
It also occurs to me that because you make a point of disclosing in your listing that you use scented cleaning products, guests might be wary that you also use synthetic sheets. In other words, that you aren't concerned with using natural products. Hence 3 people asking.