The law of non-contradiction was agreed upon by Nagarjuna’s interlocutors. Nagarjuna used it as a tool against the further views of his opponents. It was not hidden.
Saying that, “the rejection of LEM is itself a positive view” is itself an application of LEM. Which has not been agreed upon for that very reason. This is hard to discern, but if you look carefully I think you’ll find it is true. 