The specs look exactly the same on the HDX400 as my HDX900. I can’t imagine the footage would look any different. I bet NATGEO has minimums to keep out really low-end cameras. But, it’s nearly impossible to keep up with the tech specs on every new camera that comes out. I can’t keep up. There’s new models coming out weekly! Anyway, I always say, 99% of the quality comes from the shooter anyway.
Good Luck, I hope you get the gig.