I think not only is this the Creature achieving his goal known to Victor but also a precursor to the coming years of both their lives. The Creatures "grin" shows impish deviance. The Creature knows exactly what he's doing and only doing it to provoke and hurt Victor. Transitioning into taking him on a wild goose chase, leaving him food, leaving notes, making him suffer as long as possible is a game to the creature, and he's winning.