Oh? Continue. I wasn't aware of this.
Helium Backup? Or the new backup system that Google introduced..
But the latter... yeah... Back when 6.0 was introduced, Google also rolled out a new backup API. This augmented the app restore you are offered after you do a factory reset. So when Google backs up your phone's status, it also will back up any app data, up to 25MB per app, into a hidden container in your Google account (hidden away in Google Drive). When the app restores after you log in for the first time, it sucks down app data along with the stuff like your wifi config, etc. The aim here is to make the restore complete... where you will get all your config, apps and app data you had before the reset.
Now, the problem there is that Google can't force apps to use the API... well, they COULD force a dev to incorporate it as a condition to getting the app approved into the Play Store... but it is up to the app devs to use the API. If they all did, then if you got a new phone and logged in, it'd ask you what you want to restore, and you could end up with everything you had on your old phone (sans the external data like your downloaded junk, pictures, any ringtones you added, etc).
Now, I am hoping that with more and more phones getting 6.0 and above, devs will finally start to use the new API... right now, other than Google, there aren't many apps that use it. Which is a shame... between this and the Google Play Games stuff, there is no reason for an app's data to get lost on a reset...