If you open a file with LibreOffice will read the whole thing regardless of whether or not the file is on NFS or not.

The parent comment was stating that if you use the open(2) system call on a WebDAV mounted filesystem, which doesn't perform any read operation, the entire file will be downloaded locally before that system call completes. This is not true for NFS which has more granular access patterns using the READ operation (e.g., READ3) and file locking operations.

It may be the case that you're using an application that isn't LibreOffice on files that aren't as small as documents -- for example if you wanted to watch a video via a remote filesystem. If that filesystem is WebDAV (davfs2) then before the first piece of metadata can be displayed the entire file would be downloaded locally, versus if it was NFS each 4KiB (or whatever your block size is) chunk would be fetched independently.