It's very hard to believe. Besides search, Android, Chrome and Gmail are in 2B~4B range. Are there really another 6 products that are ubiquitous as these 3? Google Docs definitely doesn't have 2B monthly users. Some built-in Android apps might be installed on >2B phones, but it doesn't mean they have that many active users.
The article mentions they have six products with 2 billion users.
Google Search,
Android,
Chrome,
Gmail,
Google Play Store, and
YouTube
Also Google Maps, Google Photos and Google Drive have more than 1B users.