The gas reservoirs don't hold enough to get through a winter. They hold enough so that with normal inflows, there's enough gas in the winter - while drawing down the stocks.

You need both ~full storage and continuing supplies to get through a winter.

Sure. And still ir stands that reservoirs are filling up faster than anticipated. I'm in supply chain, and if during a period where inventory is hard to come by said inventory is replenished faster than planned, that is usually a good thing.