On: ISO3103 Tea Preparation [pdf]

[petters]

Tea (Camellia sinensis) is not an herb, i.e. not "a plant whose stem does not become woody and persistent (as in a tree or shrub)"

[OJFord → petters]

I don't know where you got that definition, but it's obviously not right. It excludes mint and rosemary leaves, for example.

[petters → OJFord]

OK, in my native language the translation of "herb" is less used in common language. The definition was from English Wikipedia though

[Tomte → OJFord]

It's the usual difference in definitions between botany and gastronomy. See: “berries”, “fruit”.