Wine's mp3 decoder doesn't work in some cases, including some mp3 files by Spotify's partners[1]. Because the decoder didn't work for some mp3 files, they are actively blocking wine's mp3 decoder for all mp3 files.
[1] I agree this is a pretty solid business reason to block it, but it's still intentional.
[1] I agree this is a pretty solid business reason to block it, but it's still intentional.