Try adding RECURSE to the first line:
Find SYNC FROM "D:\Work" TO "D:\Backups" RECURSE COMPARE=newer HIDEUNAFFECTED
Copy SYNC
Set CLEARSYNC
That was missing from the example but would usually be wanted with sync, so I'll add that to the docs. It's probably why it wasn't seeming to do anything as well (depending on the folder structures being synced).
Testing with that added, it works how I expect now.