It's a multilayered issue:

- licensing could be expired, could change hands, could be removed, could...)

- naming and attribution:

A single song by a single artist will have a gazillion versions (ep, lp, original, re-recorded, re-released, re-mastered, re-re-mastered, best hits, best songs, essential, released for the European market, released for the Japanese market, Christmas special...).

On top of that distributors and rights holders have very shitty metadata that also varies between rights holders.

So if a song changed to a different version, it's quite possible both that the contract for that song changed hands between rights holders and the new rights holder uploaded incorrect/invalid/mangled metadata that Spotify disambiguated in this way.

Or, even simpler: original metadata pointed to the incorrect version, but now points to the correct version. Which is incorrect from your point of view :)

I guess the downvotes come from people who have never dealt with licensing issues or data from content providers. I have :) The above is about 2-5% of the crap content companies (streaming or otherwise) have to deal on daily basis.

Because all of the above doesn't even begin to deal with things like territorial restrictions, content restrictions, territorial content restrictions, territorial content requirements, take down requests from commercial and government entities, rights disputes, content embargoes...

I found your comments helpful. Thanks.