Say you have songs A, B, C, D, E.
The music player being used has song shuffle turned on.
The first song that comes on is Song A. After that song ends Song D comes on. The user hits back and Song A starts playing again. When that song is over what song does the user expect to come on next?
If the app shuffles songs once at the beginning then the next song would still be Song D.
If the app shuffles every time it goes to the next song then it would be shuffled to any song other than Song A.
In practice I've seen big players like Apple Music seem to only shuffle once, so hitting back and then forward will be the same song every time. But to me that doesn't seem truly randomly shuffled. How does the average user expect this scenario to be implemented?