One amusing part of lyrics on Spotify to me is how they don't seem to track which songs are instrumentals or not and use that to skip the message about them not knowing the lyrics. An instrumental will pop up and it will say something like "Sorry, we don't have the lyrics to this one yet".
Interesting, especially that it's a probability rather than a boolean! The line can be blurry sometimes (like in the example I mentioned), so it makes sense that it might not be possible to come up with a consistent way of classifying them that everyone would agree with.
The only thing funnier than that is when they do have the lyrics to a song that probably doesn't need them, like Hocus Pocus by Focus: https://open.spotify.com/track/2uzyiRdvfNI5WxUiItv1y9?si=7a7...