Why don’t you add steam at the beginning of the bake?

I chose to do a light milk wash on mine and thus didn't need the steam. In fact, these seem to do well without any steam at all, even when there is no steam. If you'd like to add a little more color, shine, and a bit more rise, steam would help (but it's optional).

This is just a guess from a beginner-level bread baker, but I think that steam helps make the crust crispy as the bread bakes, and these buns are soft with a soft crust.