"The situation is different for Android. Google’s version of Android, which runs on most Android smartphones and tablets in the western world, only implemented encryption by default with the latest version Android 6.0 Marshmallow released in October 2015."

That version of Android is only on a handful of devices, not even a full percentage point of global market share. Even on Lollipop and older devices that do support encryption, it has to explicitly be turned on by the user. And once again, Google is not expressly clear that they don't have your encryption keys on Lollipop and lower; they only claim not to have them for Marshmallow devices. They definitely have the keys to your encrypted data on their servers no matter what, which can include complete backups of your device.

And?

> Google is not expressly clear that they don't have your encryption keys on Lollipop and lower;

They have explicitly said that if the device is encrypted they don't have the key.

> They definitely have the keys to your encrypted data on their servers no matter what, which can include complete backups of your device

Source for that?

In other words, if you can ever actually use something, it's probably not secure.