Apple Default Apps & Battery Usage

I was checking through my Battery usage the other day and noticed that my Calendar had around 12% (in the last 24 hours) and also the Notes app was listed there as well (around 4%).

I never use Notes on my iPhone 6 (I use my iPad to add notes, which sync across) and there is no way I have used the Calendar app that much - its not even open in the background.

Then, when I went to the 'Background App Refresh' setting within the 'Settings' app, I noticed that none of Apple's default apps, actually appear in the list? Does that mean that all of the Apple default apps, are always constantly working in the background, even when the apps themselves are not actually open?