Hidden 'Spooky' File Extensions

Hi. My Nextcloud instance running in Docker on a Ubuntu server stores its data on a ZFS dataset, which I take snapshots of now and again.

I’m sometimes looking at the diff between the latest snapshot and the current state and I have noticed some strange file endings showing up in the the diff suffixed on several filenames. They typically have this format .v1668092730.

However, when navigating to a file in the terminal to check it does not have this extra extension ending. So I do not understand how this would show up in the ZFS diff. As mention it is only a few file I see this on (often Note attachment images, but not exclusively)…does it have something to do with file versioning in Nextcloud? If so, how is it that this is hidden when viewed in terminal, but picked up by ZFS?

Maybe this not related to Nextcloud at all, but it would be strange because I only see this on the Nextcloud dataset and none of the other.