You might be interested in this recent thread - How to treat Spotify links to withdrawn releases?
TL;DR: Spotify has a “special” way to deal with withdrawn/unavailable releases. If the release uses a recording that is available in another release, the “withdrawn” release page will still be able to play those recordings. It’s somewhat similar to the concept of recordings in MB.
Say for example, if a single is made unavailable / is “withdrawn” but the album is still available, if you have the link to the single release, Spotify will still play the song, because it’s available in the album release, and both pages use the same source audio.
Atisket is a good way to check if a spotify release is unavailable everywhere, because it checks every country where it is and isn’t available.