>Tim Grewe, GM’s Global Electrification and Battery Systems Director, told Car and Driver that the Ultium pack does not suffer capacity loss from excessive DC fast charging, so GM will not advise users to charge the pack to less than 100 percent.

Translation: we can get higher spec cells now, so battery capacity will be over-rated. A "100 KWh" pack will be 120 KW+. When it says it's fully charged it's actually sitting at a nice conservative 80% SoC. You could fast charge it every day because the pack is so huge that 100 KW is a nice gentle 1C charge rate. You can push the warranty out further because you have more headroom for battery aging.

Presumably when the car hits three or four years old it'll set a charge threshold at 80% and start warning you about fast charging. (Or maybe not? It would be in GM's interest to let you run it into the ground like a cellphone)