Then their info is incorrect. That being said, looking at all the 16" M1 Pro and M1 Max entries on everymac, they all show "100 W h Li-Poly" for the battery capacity so maybe they have subsequently updated it to the correct value of 100 watt-hours.
Apple's tech specs also state "100-watt-hour lithium-polymer battery" with the fine print being "99.6 watt-hours"..