I'm sure that @HighStream read and remembered that point, and would have otherwise been able to infer as much before the skeletons were shown. It is still unusual that the remains of the children were in the view-frame.
I think that the skeletons were shown to insinuate that the actions of Luck did not cause any of the children to be reduced to dust.
Wow. Child skeletons are...strangely disturbing compared to adult ones. I'm not sure how much I want to break down the underlying reason for that, but...well, it's effective, one way or another.
@Tensei21 He fought for 10 years straight, most of that time with a sword. He couldn't have used magic for all of them, so he probably got a lot of practice with the blade, especially for the weaker ones.