The footy bit that holds the magnets for the bottom case also has a mystery cable locked inside it.

Closer inspection reveals: yet more mystery!The cable sports four contact points. Perhaps more testing points?

Alternate (totally made up) theories:

Recognizes the color of the base, so the Home can coordinate its outfits better.

Vestigial charging mechanism. (Maybe the Home's architects intended it be a portable device?)

Abandoned easter egg dungeon level for teardown engineers.