> I'm confused, I've restored Signal from encrypted backups before. I did it like 4 months ago. What's this feature?

Those backups are stored locally, are platform-specific (Android-only), and there is no feasible way to automate their transfer to any other device, which means that either you have to manually manage them regularly, or you risk losing your entire message history if your phone suddenly dies (or is stolen, or broken beyond repair, etc.).

This is a true automated, off-site backup feature.