This is one of the most popular methods to handle apps that are using a storage backend directly over the internet for increased bandwidth, and separation of deployment and state.

If I'm hosting something like Nextcloud at a massive scale, it simply isn't feasible to use internal networks because they don't have enough bandwidth, and overlay/vpn network solutions have too much overhead. A common solution is to just run the services and directly connect to them over the internet. So I point my 10,000 node Nextcloud instance at S3, either my own cluster or somebody else's and S3 handles encryption while remaining reasonably performant. And scalable.

Garage uses their software internally for something similar: https://garagehq.deuxfleurs.fr/documentation/design/goals/ . On this page, they describe using it as their matrix image/file storage cache. Same thing there, they probably have a large distributed matrix cluster that needs storage that scales with it, while also being secure over different networks.