It calls itself "the Ark second-layer payment protocol"

That is different from calling itself "the payment layer," as if there is no other

There is no other second layer payment protocol called Ark so it is perfectly reasonable to use a definite article ("the") in order to distinguish this layer two from other second layer payments protocols called other things (e.g. lightning)

You sound upset, why? What is wrong with more second layers? Devs are just devving my friend, it's what we do