The Overall section at the end of each questionnaire serves as a general indicator of parental concerns. Any concern about development noted by parents should be discussed with the parents, and a referral should be made if appropriate. Keep in mind that these questions are not diagnostic; they can only serve as a guide for discussions and the potential for further assessment.
In the situation you described, a child may pass many of the expressive items in the Communication area and receive scores that are above the cutoff point. However, the child's parents may have noted concerns when responding to the questions "Do you think your child talks like other toddlers his [or her] age?" and/or "Do other people understand most of what your child says?" and a referral may indeed be warranted.
For a more detailed explanation of the ASQ-3 Overall questions and possible indicated issues, please refer to Table 6.3 in the ASQ-3 User's Guide.