I think you may be on to something there. If I search for James Taylor, there are a whole bunch of them. The first James Taylor is the one we all know. The second one has his picture. If I select both of them after a search, the merge function is available. If I select any of the other James Taylor other than the first or second, no merge is available.
Oddly, the ‘second’ James Taylor listed has the “James Taylor” artist in circle from the search. When I click on it there is also a picture of the most famous James Taylor, but no bio. All of the albums seem to be from another James Taylor. So while I could merge them, they are two different artists.
All of the other James Taylors that can’t be merged just have the JT in a circle, and they seem to be references to music that was also performed by James Taylor.
This situation is best characterized as a ‘dog’s breakfast’. Don’t know how that translates to Dutch, but this is a mess of metadata.
As @BrianW said, it appears to work on the results of a seach when the underlying meta data are well behaved.