The only thing I found stupid about the trailer was that cheif had different armour.
Also shield world?
Halo Wars had a different approach as well. Plus they don't use the same files as Bungie, they probably had to remake the whole model from scratch.
Now, the stupid thing you should of underlined is that John had a jetpack in that scene.
Also, it very well could be it. If that's the case there is a good chance that John's team members may be lost there, unless the only remaining thing is their armor silently laying on the edge of a cliff together, hollowed out empty.
Honestly I would literally yell "NoooooOOoOoOoo!"