Very true however unless N3V have a crystal ball there is no way they can identify the name of an item that is not and never has been on the DLS and is not in their database and that accounts for many of the missing assets, a name is extremely unlikely for anything not on the DLS or builtin.
But....... Things are not always as bad as it might appear. Right click list asset Versions, sometimes yields a result as in a newer or older version or sometimes an item that obsoletes it.
This appears to be caused by gaps in the versions uploaded, if the base item isn't on the DLS but it starts at say kuid2:xxxxxx:xxxxx:13 then the right click, show versions method is often the only way to find it, that is one problem that should IMO be addressed although as it seems to be getting better of late though, maybe they have?
Items on the Repair list may not show in manage Content or show as location unknown or third party as they are in some way faulty in one or more builds, however you can usually download by using Custom and input the kuid number if you know what it is or get it from the White pages.
and
Often I've found location unknown will actually download if you try it.