iOS 11.3 battery health already lying?

As a consequence of the Apple's Battery Gate, Apple introduced "Battery Health" information in iOS 11.3, and is displayed as a beta software.

I'm using an iPhone 6 bought more than 3 years ago, still using the original battery so I was a bit suprised to see that "Battery Health" is showing that my phone has currently a maximum capacity of 100 %, like brand new:

So I fired up coconut Battery with which I have been monitoring my Mac and iPhone battery for a while:

Here we can get more details, the battery has been through 453 charge cycles, the original battery capacity is 1810 mAh but now it holds 1712 mAh at maximum, so 94.6 % of the designed capacity. Which is still pretty good for a 3 years old battery. According to Apple, the battery is designed to hold up to 80 % of it's original capacity after 500 charge cycles.

So what is the "Maximum Capacity" percentage shown? It's not explained in any of the pages I have read on Apple's website. My iPhone's battery is in good health but not 100 %. It should have been approximately the same value as the one provided by coconut Battery, but obviously it isn't.