It isn’t that children with ASD/ASTD can’t lose focus: when they’re doing things they do not enjoy or hearing about topics in which they’re not interested, they have no trouble losing focusing and returning to the task later. But when the task is repetitive or boring, they keep focus and fail to tune out.
Failing to stay on track is another common problem. Children with ASD/ADTD often bounce from task to task and are able to comple all of them, or skip unnecessary steps in procedures because they are not prudent. Organizing their schoolwork and their time is easier for them than it is for most children.
Kids with ASD/ASTD also diligently concentrate if there are things going on around them; they usually don't need a calm, quiet environment in order to stay focused.