yes, this part is also mounted at the Y1 models !
Without it, chain hits the side of the tire.
That is a known issue here.
You may imagine how the side wall of the tire looked on my Y1, without this guide and a wider 150/80-16 tire mounted !
That tire size is legal in Germany on rear stock rim 3.00×16, but not recommended by me for riding purpose !
It is just for the “better” look, not for better riding 😉