It's not totally related to SM I guess. Even in his fight with the raikage, he was in SM but he used a clone. I think he improved his chakrs control, so he can do it with one hand now, at least in SM. This shows that he improved, so he should be able to do it in base form.He was in sage mode.
that's impossible:|Yep his chakra control is better than Sakura's now.