MC11.1 has no problems in placing new cover art files according to the selected option.
The problem is with mass changing old cover links. MC has excellent tools for moving library files, but traditionally the cover art files are not part of the media library. Inside the database a cover art file exists only as a link in one of the library fields.
Basically the idea I explained in this
post is to import the images and use standard MC tools for moving them just like MC users are accustomed to move their other media files.
At first sight those six steps may look complex, but there is nothing that many MC users don't usually do. After the old files are moved the problem does not exist anymore. Though, in case your music files are not in the Artist\Album folder structure the instructions need to be adjusted and the process may not be as straightforward.
Alternatively, you can move the files outside MC with a suitable file handling utility. MC can find the cover art files automatically from the file folders (do first "Image > Remove Cover Art", then "Image > Quick Find In File / Cover Art Directory").