Look, it makes no sense to establish a feudal monarchy in steppe territory, so releasing nations of your own government type itself is not really balanced or historically plausible. And some questions: Should a merchant republic release an administrative or a noble republic in horde territory? Does an empire release a feudal, a despotic or even an administrative monarchy? You can argue for or against all those things and anyone would always complain. For me and probably 99% of the players its acceptable to release those nations as tribal and if its not okay for you: Deal with it, nobody cares (sorry for the rude speak but its probably a fact).
So sure. Let's have it that way. But then it must be that way for *all* government types.
I don't care if merchant republic/empire release tribals as tribals if the rest of them also do.