Which is very similar to how SSDs work. They all include buffer capacity so as the NAND blocks die off, the user never notices. So the 1TB SSD may contain 1.5TB of NAND inside, but you don't know, and you don't need to know, as long as it keeps delivering 1TB of storage.
Different companies have different levels of transparency about battery state-of-health, and there's no standard right now to make sure you can compare between manufacturers. Tesla tends to report state-of-health that drops from 100% relatively quickly into the 90s in the car's life, but then stabilizes at a slower degradation rate over the long term, which is close to the truth about how batteries actually behave. Ford tends to report 100% state of health for a long time. It's easy to assume that Ford thinks the consumer expects their "new" car to stay new for a long time, so they want to show 100% state-of-health to avoid spooking customers and reduce warranty or trade-ins. In reality, Ford just programmed in a certain amount of buffer capacity into the life-o-meter so the customer THINKS the battery is at 100%* health (where 100% is defined as e.g. "above 90%"). Ford doesn't have better battery technology than Tesla, they just have better marketing.