Not downloaded relations are shown on the list if they are part of downloaded relations

[Daeron]

If a relation that contains other relations as members is downloaded, the member relations will be shown on the list, and can be freely edited. They are shown as having 0 members and no tags, which will lead to data loss if the relations are edited and the modifications are then uploaded.

The Download incomplete members function in the relation editor doesn't download those relations, implying that josm thinks they are not incomplete.

[Daeron]

Seems to have been fixed in [2579]