Even many dry Brut Champagnes receive a small sugar-and-wine dosage after sediment removal; why isn't that simply a trick to make them sweet?

Answer: To balance sharp base wine

To restart the bubbles — Dosage happens after the second fermentation and disgorgement, so it is not the normal engine for making bubbles. The pressure and fizz are already there. If a winemaker wanted to restart fermentation, the bottle would face new sediment and pressure-control problems, which is exactly what the previous steps were designed to finish.

To balance sharp base wine ✓ — Right: dosage is a final tuning step for balance and house style. Brut Champagne can contain less than 12 g/L sugar, far below dessert-wine territory, and the acidity and CO2 can make that small amount read as balance rather than sweetness. The counterintuitive part is that adding sugar can make a wine taste more complete without making it taste sugary.

To make it dessert-sweet — Brut is specifically not dessert-sweet. Official Champagne categories put Doux above 50 g/L sugar, while Brut is under 12 g/L. That gap is why the same ingredient, sugar, can mean very different things: a tiny seasoning in a sharp sparkling wine, or a genuinely sweet style when used at much higher levels.