Your example is not the same. The argument isn’t whether or not producing nitrogen is necessary. The question is whether how we produce nitrogen is necessary or

Your example is not the same. The argument isn’t whether or not producing nitrogen is necessary. The question is whether how we produce nitrogen is necessary or if there is an alternative. Using your example, it’d be like if we produced oxygen using process X and then saying “process X was necessary to save the species because we would have run out of natural oxygen.” And someone saying “Not necessarily because process X might not be the only way to produce oxygen.”