Technically both are correct…
Technically both are correct.
The Ford Mach e and Lighting both have a buffer built into the battery. It just so happens that buffer is 10%. So even charging to 100% according to the car, the physical battery is only at 90%. Setting a Ford to charge to 90% gets you pretty close to 80% of the physical battery.
Ford did not come up with their own charging guidelines, they just limit the usable amount of battery to prevent damage.