Going all the way to 100% doesn't automatically damage your battery. It's charging it to 100% all the time, and also operating it at 100% at long periods of time that reduces the lifespan.

I'm sure there's some arithmetic where more accurately charging to 80% instead of 85% wins out over never going to 100% in terms of battery life. Not saying Apple engineers did this, but I wouldn't assume they hadn't.