What primary benefit do lees provide when stirred into wine during aging?

The primary benefit of stirring lees into wine during aging is that they enhance flavors and mouthfeel. Lees are the deposits of yeast and other particles that settle at the bottom of the fermentation vessel after fermentation. When these lees are stirred, or "batonnage" is performed, the wine comes into contact with the dead yeast cells and other compounds released into the wine.

This interaction contributes to a creamier texture and can add complexity to the flavor profile of the wine. The process can introduce notes of bread, toast, or nuttiness, which are often desirable in many styles of wine, particularly in white wines like Chardonnay. Additionally, the increased contact with the lees can help soften the wine, making it smoother and enhancing the overall mouthfeel.

While the other options mentioned may have their own relevance in the winemaking process, they do not directly align with the primary benefit associated with stirring lees. For example, lees do not significantly accelerate fermentation nor do they increase the alcohol content, and while they can play a role in clarification over time, that is not their primary purpose when stirred into the wine. The focus on flavor enhancement and texture improvement is what makes this practice highly beneficial in winemaking.