My theory:
(I haven't seen the film yet, so I'm going on what I know)
The factory is the T-700 factory, hence the texture of the metal because it is not designed to have flesh over the top, and the color of the teeth...
Even if they were T-800s, those teeth would need some serious recoloring...
The T-800 that they run into is a prototype, a new design, hence the other name T-RIP, or Terminator- Resistance Infiltration Prototype...
There's no doubt the T-800 was built as an infiltration unit, look at the future Terminator in T1, and AHNULD in T3 (although he was a T-850, but it's the same model series).
The reason people are getting confused is because Hot Toys got it wrong. The T-700 is meant to be bigger than the T-800, if only slightly, in fact, so little that when they are spied in the films, it is hard to see any difference in size at all...
Marcus Wright is an Infiltrator Model, but not like the T-800. In the books and comics, there were other models who had the same origins he did, one I remember was an I-950...
So I think that there are T-700s in the film, and just the one T-800...