Out-of-universe; Although the soundtracks were different in the original versions of the game (Japanese and US), there is something to be taken with the US soundtrack. The Past tracks, which are shared, represent what was originally going to be in every version of the game. The Present represents what changed through No Export for You-esque circumstances, and the Futures represent that the changes were persistent and will evolve, as the Sonic Gems Collection shows. (Not implying that Gems changed the music. Just noting that it has a version of Sonic CD on it. And it was released after Sonic CD, therefore, the future.)—Akamia
Better than that. It also hints that somewhere along the way, there was a Split Timeline event, which after the Past, changed the music for the Present and Future.
The Japanese boss theme samples "Work That Sucker To Death". In Quartz Quadrant, you defeat Eggman's conveyor belt contraption by running the belt until the console platform Eggman is standing on wears thin and he's forced to flee. In other words, you literally work that sucker to death.