What information is implied by the non-assignment of a taxon to any realm?

As of the time of writing, one class, 19 families, and two genera are not assigned to any higher ranks. What information is implied by this non-assignment? I presume it is supposed to be understood in one of the two following ways:

  • An unassigned taxon is incertae sedis; it may or may not be related to other viral lineages, but further research is needed to make that determination.
  • An unassigned taxon represents a unique lineage that has no evolutionary relation to any other viral lineages, but is not assigned to a realm by itself, due to a lack of known diversity or the assignment is pending.

Which is correct?