The buttons "Add Folders" and "Move Content" have been added to the UI as part of the Winter'21 release.
See the release notes https://releasenotes.docs.salesforce.com/en-us/winter21/release-notes/rn_cms_folders.htm
I have been able to replicate and confirm this behavior in my Summer'20 and Winter'21 Orgs.
If you only ever want the most recently modified Knowledge Article you can order your results with an ORDER BY clause. Otherwise the result you get back may as well be random. The LIMIT 1 will ensure that only the first result out of that ordered list is returned.
WHERE Id IN (SELECT ...