I suppose they can advertise a 0.9x Wh battery and include a 1x Wh battery instead, which is fine for me. If the battery is going to degrade hard just give me one that only reaches 90% max.
My old 2018 Hyundai Kona EV did the same thing: officially it was a 64kWh battery, yet when you count the cells they come out at 71kWh or something. They built in some margin to extend battery life as capacity declines. Coïncidentally this also meant that regen braking worked even when the battery was 100%. The car is at 110,000km and the BMS still reports 100% SoH.