While enabling Drive backups is something that the user has to enable manually, I'm not sure the complete consequences of doing so are really communicated to the user. I wouldn't expect Google having an agreement bypass to access my messages even if Drive backup was enabled, but that's exactly what happens, if I understand it correctly.
> Media and messages you back up aren't protected by WhatsApp end-to-end encryption while in Google Drive.
https://faq.whatsapp.com/android/chats/about-google-drive-ba...
While enabling Drive backups is something that the user has to enable manually, I'm not sure the complete consequences of doing so are really communicated to the user. I wouldn't expect Google having an agreement bypass to access my messages even if Drive backup was enabled, but that's exactly what happens, if I understand it correctly.