At face value it seems less advanced and less stable than Rex, Rex was awkwardly designed, but it moved way faster and had better weaponry, it was a freaking tank, Rex would rekt Inbred Rex no problem, but, what really distracts me is obviously the fact that the aesthetic is completely out of place and does look more "advanced", at least more stylized, and the sword, which got me thinking and it suddenly hit me...
what if it's a hallucination? Considering kid Mantis is floating next to it, it would be consistent with the other hallucinations seen in trailers including skull face, the whale and more, what if that also has to do with the weird cloudy eyes some characters are seen with?
What other way would you explain the aesthetic clearly out of place with the series when even D-walker fits right in? I don't believe Kojima would just make such an abrupt change in aesthetic at the last minute
I put it in spoiler tags just in case, it's just a theory it occurred to me last time I watched the trailer, it would certainly explain the weird aesthetic and sword.