Q:

Is Android's "Auto Backup for Apps" also a sync tool?

Starting with Android Marshmallow, your app data will automatically back up to Google Drive unless the user's opted out. What I'm curious of is if you have two devices that you use regulary - how does Google resolve sync issues? Will both devices reguary check for changes in the backup data, or will they only check on installation? 
In other words, is this a sync tool or a backup tool?

A:

The Auto Backup feature will backup on a daily basis for use when you install the app on a new device.  It won't sync unfortunately.  
I'm guessing if you have the app on two devices the latest changed data file will replace the one held in the private Drive app data folder.  They can't merge them as Google can't determine your data file format/structure/relationship rules.

