From en.m.wikipedia.org/wiki/Herbal_tea :

… most dictionaries record that the word tea is also used to refer to other plants beside the tea plant and to beverages made from these other plants. In any case, the term herbal tea is very well established and much more common than tisane.

Furthermore, in the Etymology of tea, the most ancient term for tea was 荼 (pronounced tu) which originally referred to various plants such as sow thistle, chicory, or smartweed, and was later used to exclusively refer to Camellia sinensis (true “tea”)