It's not clear what that actually means though. Consider this: every iPhone that has an active data connection regularly contacts the App Store to see if there are updates(i) to apps, regardless of whether or not the user actively visits the store. Are these update checks counted by the graph? What about system updates? Are those counted as going through the App Store?
Regardless, we can be relatively sure that that graph is there to help developers when deciding which versions of iOS they should support. It would not be surprising if Apple decided simply to include only active App Store shoppers, because this is the number that actually interests developers.
(i) I'm not actually sure if this is true if you have never installed an app from the App Store - there is maybe an exception where these phones don't check for updates in this case.
Regardless, we can be relatively sure that that graph is there to help developers when deciding which versions of iOS they should support. It would not be surprising if Apple decided simply to include only active App Store shoppers, because this is the number that actually interests developers.
(i) I'm not actually sure if this is true if you have never installed an app from the App Store - there is maybe an exception where these phones don't check for updates in this case.