I agree with you, of course. On macOS, Arq uses APFS snapshots, and on Windows, it uses VSS. It'd be nice to use something similar on Linux with restic.

In my linked post above, I wrote about this:

"You might think btrfs and zfs snapshots would let you create a snapshot of your filesystem and then backup that rather than your current live filesystem state. That’s a good idea, but it’s still an open issue on restic for something like this to be built-in (link). There’s a proposal about how you could script it with ZFS in this nice article (link) on the snapshotting problem for backups."

The post contains the links with further information.

My imperfect personal workaround is to run the restic backup script from a virtual console (TTY) occasionally with my display server / login manager service stopped.