It doesn't quantify winter range. It gestures at possible benefit; without comparison to the state of the art, it's not especially meaningful. Nevermind that losing less than 10% of 250 miles is not a ton of range.
The absolute range is not the point. You can increase absolute range for any battery by having a bigger battery. The point is the low percentage lost due to cold.
Again, it does not compare this against the state of the art. We know how to heat battery technologies that are more sensitive to lower temperatures. So the interesting question would be, how does the combined efficiency compare? No such comparison is made.