That's certainly a useful sniff test, and I think you've made a good case with it. I wonder, though, whether one should also consider a "documentation sniff test", asking: would it make sense to type that symbol into some documentation one is writing about how to use, for example, some software? I think the answer to that question is a clear yes: it might make sense to put this symbol onto such a page, and although being on inert paper (it wouldn't also be an active element) it would certainly be a useful symbol in that hypothetical text.