I think equanimity arises as a result of the metta practice. Just like joy can arise spontaneously. It's all intertwined and not really that separate, also with other practices outside of the brahmaviharas. So no special need to practice it specifically. For me at least. Also, I think equanimity is mostly a result of insight and not that much of a specific practice such as metta.
As I read those instructions they are also part of metta.