How useful is floating a teapot in the air to serve hot tea?
Although both tea and wine have tannins — in varying amounts depending on steep time and prior to separating grape juice from the stems and skins in the case of wine — the former hardly needs to be aerated. Height is not necessary in the pour. And even if it was, a human could do the same with an equal amount of training.
What is the exact purpose of Diana Cavendish floating her teapot over to her teacher other than to pass her exam? Does she offer a service that couldn’t be provided by human hands?
No, she does not. The action is essentially useless.