I used the “SM_Crypt_Floor_Concave” mesh in some places and added a plane with a water texture to add some puddles. Here is what I got with the original texture (with pixel depth):
I think it looks pretty nice (although the puddle is a bit too bright).
But this is what it looks like without the pixel depth:
(note also where the ground meets the door frame on the left)
Welcome to the '90s and their low-poly engines!
While the ground texture is not the same as the one for wall from the video, the difference is done through material instances. They share the same parent material. So fixing one affects the other.