I did look around a bit, there seems to be a specific version to download:
If you go to the 3.13.2 version on assets, you can download the Nextcloud-3.13.2-macOS-vfs.pkg
I don’t know if this file is different from the file over the download links from the Nextcloud homepage.
It seems the VFS feature was planned to become official but there still have been a few issues so it wasn’t rolled out so far.
A bit of background about rolling out the feature, check the details yourself and if it makes sense for you to test the feature:
https://github.com/nextcloud/desktop/discussions/6656
and some plans/thoughts about a dedicated mac client: