That common side should just not exist if both were outside because they would be one parcel with no dividing line. If one parcel has been identified, the identified parcel is of the opposite type. An identified outside connected to an identified parcel by a section line usually indicates the other parcel is outside. The rare exception is when one side of an inside parcel is a section line and is connected across the section line to a lot. Joining inside parcels to identified parcels to create a bigger parcel may result in a parcel with only special point ids.
All parcels included in it are inside.
This occurs when a series of interconnected mineral surveys crosses a section line. The hardest identification is along the township exterior because the data ends at that place due to the way GCDB data is stored in unique townships. Due to intersections of lines, it is entirely possible that a special parcel from raw data may be made up of several subdivision parcels. The aliquots are easily identified from their point ids. What is left to identify are the specific lot numbers for the identified lots, lots which replace an aliquot identification because it borders a closing line, and specifically what the special parcels represent.