I want to claim adoption expenses for adopting my grandchild who was born in December 2016 who is not disabled. Why do I need to check the disabled child checkbox?

My grandchild lives with me and the adoption was finalized before the end of 2016. She turned 18 in December 2016 prior to the adoption being finalized.  I am being directed to put a checkmark in the Disabled Child Checkbox on Form 8839 "Qualified Adoptive Child Worksheet", but she is not disabled.  Can I claim credit for the attorney fees and court costs related to the adoption?