Google Drive horror

I’m not on Android currently but a person I often talk to is.
We send messages encrypted since we both use Delta.
I remember reading about an issue with a competing, proprietary app that claimed to be e2e but then the locally decrypted messages were stored plaintext in Google Drive via some sort of backup thing. Is Delta Chat on Android susceptible to something similar?

This is what WhatsApp does, nagging the user until they accept to backup their chats to Google Drive.

Delta Chat does not do this and explicitly opts out of being backed up into system backup via AndroidManifest.xml: