Looking at the "recovery" sub-forum you mentioned, it looks like it is not configured as a wiki sub-forum. By looking at the forum listing on the index, it shows a regular forum icon, rather than a wiki icon. When viewing the contents of the forum, all of the threads have showthread URLs rather than wiki URLs. This explains why the old wiki URLs don't work.
If you moved wiki articles to a non-wiki forum in VaultWiki 3, those articles lose all wiki properties and are only accessible by their showthread URLs. This is expected behavior in VaultWiki 3. You are correct in your assumption that such normal threads would not be imported to VaultWiki 4, even if they were wiki threads before they were moved.
To regain wiki functionality, you would have to convert the forum to a wiki forum in the forum settings. All previous wiki data on these threads was already lost, so they would start with exactly 1 edit (the current edit) and no other properties yet.
I'm afraid if there was a bug in VaultWiki 3.x, it will not be fixed in VaultWiki 4.x since you can't even do this in VaultWiki 4. Likewise, it would not be fixed in VaultWiki 3 because VaultWiki 3 is long past EOL at this time.