When the Music app is streaming a live source such as Apple Music One, Apple Music Hits, Apple Music Country, or Apple Music TV, Music MiniPlayer will display a simplified UI that complements the limited options to live streaming audio.
For example, the previous and next buttons are disabled as well as the scrubber, shuffle, repeat, and time stamp options are all replaced by a "Live" label.
If you play a local track or stream an album, the standard user interface will return.