Sure, you can probably build something similar with zfs snapshots, but it’ll likely not be as convenient. Have a VM? Create daily snapshots. Break something and can’t figure it out? Just reset to the last backup to a complete working state.

Personally, I have the containers’ mounts in the VMs (ergo on the nodes’ disks) and just using the NAS for the backups. Even if both Proxmox nodes catch fire I can just import the snapshot to a new one and have a working VM in the same state again. That’s a whole different level from re-cloning all the compose stacks, mount NFS shares etc. It’s the ease of use.