New top growth often appears long before roots. It’s the same as a stem in a vase producing new leaves. Rose cuttings are far better rooted in a soil mix or potting medium than water And even in soil it takes time.

The canes are simply using the food they have stored in those canes to produce new growth instead of roots. Chances are they will not root now. As floral said, they prefer some type of soil to encourage rooting. And using a rooting hormone will help too.