I have a 2001 and I don't know if the sprocket cover and "separator" are exactly the same or not. (I'll call it a separator because it sure ain't a protector.)
I saw some superficial marks on my the separator and looked into it a bit. With the bike in the air and the suspension fully extended the chain can rub on the back lip of the sprocket cover. And it's hard to see the front of the sprocket with the cover on so, for a while, I thought I could hear the chain hitting the separator.
In the end I decided that the marks were from when the chain is loaded with clay and crud and that the chain doesn't usually hit the plastic. The superficial marks haven't changed much in 10 or 14 thousand miles.
I can see how these pieces of plastic can each flex a little differently so one may have contact where another does not.