The chest BD should technically get worse during final battle when the t-1000 rams the iron into the t-800s chest. I actually always thought it was that scene that rips the skin off his chest to reveal the hyperalloy combat chassis but am wrong (even though I've seen the movie a million times haha). But it seems the movie just uses the same BD chest during the shootout scene lol. Prime 1 may have corrected this and made adjustments and lowered the BD level on the chest for 'realism' and aesthetics sake. Similarly the BD on the head, in the movie it was glued on and made arnies face look puffy but obviously this has been corrected on the statue. I guess prime 1 dialled back on these to make the statue 'work' and look more realistic?
The minor knee damage appears to be more of an aesthetic balance on the statue.
If they go 100% on knee damage, then I guess its not so much a police shoot out but more of a hasta la vista baby scene. If they go zero knee damage that is more accurate but arguably it could look less cool.
Prime 1 went in between in all of these on the platinum (head bd, chest BD, knee BD) to strike a balance it seems. I think they have made the right choice, lesser chest and knee damage (whilst not fully movie accurate) looks better and is likely what the movie wanted to portray but special effects team may have gone lazy and gave Arnie the same damaged chest lol.