No extra space was used.
You can verify with this:
sudo zpool list -o name,bclonesaved
The “consumed space” you’re seeing is just how a file/folder is reported by Windows File Explorer (or even when assessing the contents of a local directory on the server itself.)
Such file tools are unaware that “blocks” on a pool that are being “shared” by the same file(s).[1]
This is not to be confused with “hardlinks”, since the resulting files after a copy (via block-cloning) are completely independent of each other. If you modify one of them in-place, it will not affect the other. ↩︎