Yes, it's perfectly normal, and I think it's even documented in the manual. cp and other programs make the assumption that if it's the same inode, the files are identical, and due to the way snapshots work, it's the same inode. Copying it from what looks like another filesystem to the client is the easiest way to get around it. If you don't want people accessing the snapshot directories that way, just mv or remove the old file first.

Bruce