nisht is correct.
I don’t think they should have granted the request. But they should have said that they looked into it and are satisfied that the FDA’s response is correct.
Not just “oh, that’s the FDA’s job”. The FDA works for the president, and answers to him. He appointed the head of the FDA, and can fire her. The whole point of the petition page is to call the president’s personal attention to particular issues that people care about. But he just says, “oh, not my job”.