Relative to well adjusted/normal adults, yes. Obviously they're referring to children with poor self regulatory behavior relative to other children. Were you actually confused about this, or just doing the thing everyone does where they see if they can poke a hole in a study without actually reading it?

In comparison to adults? Of course. That's not the question at hand. Add in the comparison of abused or neurodivergent children to the regular child mix and you've got yourself a study.

Challenging assumptions with evidence is science.