As of the latest 13.4 software update, the HomePod runs tvOS, Apple’s operating system for its TV set box. Until now it had been running iOS. References to two new models of the HomePod were also found in the code, a HomePod Mini being one possibility (via 9to5Mac).
What Does That Mean?
iOS also has different power consumption management than tvOS. Since the Apple TV and HomePod are devices that are always plugged in, HomePod running tvOS should help bring improvements to power.