Basically the command is misunderstood by most users.
It is not intended to generally identify geometry.
The command requires that the objects be highly modified to be recognized as special enough to watermark.
There is a lot of talk about removing the command because of this general misunderstanding.
If the problem you’re trying to solve is to make it so your designs can’t be easily modified by another Rhino user, then a good approach is to make well-fitting meshes from your NURBS geometry, and export the meshes to your down-stream user. Don’t send them NURBS objects that can be easily edited.