This issue is related to single-player mode only (no LAN opened).

Jukebox music pause when game is paused with "Escape" (that's a fact).

When the advancements menu is opened, the game is paused (that's another fact).

However, the music from a jukebox still plays in the advancements menu, which is illogical (how can this jukebox play if the game is paused?).

This is simple to reproduce:

Place a jukebox and put a disc inside, then open your advancements menu. You'll hear that the music still plays.

Music is powerful. It cannot be stopped.