If the ownership of an item is shared organizationally and reassigned to a group with an admin who is not a member of that group, the admin is unable to see the group listed under the sharing properties of that item.
The behavior that is listed in the bug details is no longer reproducible. Please note that "When you transfer the ownership of an item shared with one or more groups, the new owner must be a member of all groups with which the item is shared." Refer to https://doc.arcgis.com/en/arcgis-online/administer/manage-items.htm#ESRI_SECTION1_F9D72CA4252E4EB18F4B081C27ADF527 for more information.