I suspect the Google/Facebook deal for "free backup of WhatsApp chats on your Google account" is exactly that.

WhatsApp had perfectly usable encrypted backup - which took up space on your Google backup. And then, all of a sudden, it wasn't encrypted and didn't take up space. But you don't have access to it yourself - only Google does (and WhatsApp if it is recovering). This is a perfect way to provide all the data to various governments for 99.9% of users, without killing the E2E encryption.