Yet if that beautiful teapot form pours poorly, or the handle is uncomfortable, or the lid falls off unless held on, or the tea gets cold too quickly, of what use is the teapot except to sit on a shelf.
Isn't all that a part of form? No amount of surface decoration or pretty glaze is going to fix that.
So maybe a question might be, 'Is how a item operates a function or form?' I'm thinking it could be argued either way.