.dat low poly 3d models

Something Ive noticed about the 3d models in the portal.dat file is that some models have 3 versions (as seen below).

My thoughts on why that is:

- The client calls in lower poly models when a player sets their graphics settings lower

- The game loads lower poly models in the distance. In other words the farther an object is from a players camera, the lower the poly count is on the object.