The tea plant is camellia sinensis, so technically any tea not made with a plant of that species is not tea by the original definition. All the different kinds

The tea plant is camellia sinensis, so technically any tea not made with a plant of that species is not tea by the original definition. All the different kinds of tea are the same bush that is grown in different conditions, the leaves are harvested at different times and then processed in various ways. The significance here is that they have discovered a variant of the tea bush that is naturally caffeine free, while presumably retaining its other qualities and taste. The word tea has been with us for about 4 centuries now, so it's no wonder it has taken meanings other than its original strict definition. Herbal tea would have been called a potion before the word tea was introduced.