My only point is that membership on any practical level is based on registration and not territory. Since there is no canonical definition for registration, its not a canonical issue. A parish may be defined geographically, but actual religious practice is not (aside from the aforementioned Sacraments).
This really boils down to semantics, since there is no Canonical definition for “parish membership”, only for territorial jurisdiction of parishes, which also includes non-Catholic Christians in the area. Obviously they would never be considered “members” of the local Catholic parish.
Peace and God bless!