No it's device id first (anonymous) then either facebook or email to secure the account. Given the target audience, google auth probably wouldn't be popular.

DeviceID is not anon.

It's anonymous in the sense that the account is tied to the device and not the user. It's also anonymous in the case of platforms like Apple where the device id is unique between different publishers. Note this is a widely accepted way to refer to device id type accounts on mobile.