These are just standard OBJ files with diffuse textures only and trivial material settings (all white). Additional there is some metadata that specifies that the same data is to be used as displayable model and collision geometry.

So, essentially, this data is highly portable, photoreal aesthetics is not really a goal. (Also see some notes in the paper, e.g. "Limitations of the Dataset".)

I think it's great to see Gazebo acknowledged here. I've often wondered why it's not more often considered for the basis of RL systems, as it is designed for robotic simulation, and supports multiple physics engines.

It has nothing to do with photorealistic rendering.

The pictures of the scanned objects are put on the 3D model.

  > Interesting choice.

Things like this are often not "a choice", as in twenty engineers did not sit in a room and discuss the merits and drawbacks of each format. Rather, they are "a doing", as in the intern tasked with scanning the object used the first tool that appeared in his DDG search.