My understanding on Li-on batteries is that they don't like to be charged to 100% capacity and that it can prematurely degrade the battery. Something to do with voltage increasing and heat at the last 10% charging capacity? Do Samsung allow their batteries to be charged to an actual 100% capacity or do they actually only charge to 80% but appear as 100% to the user/consumer?
First, a battery is not like a watter bottle with a clear, definite capacity. It's more like a balloon that you can charge more than it's designed for, but if you overcharge it, it gets damaged. There's a threshold that the battery manufacturer thinks "safe to charge to", and that's what you're presented with.