Battery status shows background activity but background app refresh and location permissions are off

As an iOS developer, I am extremely curious about this case: Battery usage on my iPhone 6 (iOS 8.1) shows that the main reason of battery draining on my phone are Facebook and Twitter, both have a label "Background activity" below their names.

I used to think, that this label is shown when the app does background app refresh, but that option is switched off on my phone. There is one other way to have the app run in the background: background location updates. Since neither of these two apps have this authorized at me, this can't be the reason. (And GPS icon was not shown either.)

So my question is: How is it possible to have Facebook and Twitter app running code in the background without background app refresh and location permission?