The multiskip just helps you select a family line if it appears that most of them already exist on WikiTree. GEDCOMpare isn't a thorough search so it's likely to miss duplicates. The goal is that it will find at least a few of the members of a family. Then you can look at the family members' profiles on WikiTree and see if they're all there. If they are, use the multiskip selections. If they're not, you might just want to skip the individual.