I guess I don't know the back story, but the OP had some good points about the interior. I was brought to this thread because in my researching of the WRX before purchasing I just found out that the interior is two toned. I've only been in a new model STI and never a WRX, so I didn't know this and never would have thought this would be the case. It's definitely an odd design decision considering black is the only interior option so it's not like it needs to match other colors, and even weirder is that the black parts are already made for the STI so Subaru wouldn't need a new process to make the parts.
I haven't bought a WRX yet, but am heavily favoring it now, so I'm trying to plan out what I would want to do to the car to get where I want it to be. I wanted to sound deaden the interior and add an aftermarket Pioneer stereo. Now I will likely add this change to the list. I'm a bit hesitant to paint and mess with the interior of a brand new car though, so I would at least want to get the fabric pieces and the parts that people would touch be authentic parts. This seems expensive though. Looks to be about $800 in parts.
On the plus side it will give a reason to sound deaden the roof, which I wasn't going to do.
I will look into that SEMS stuff for the parts that don't need to be handled to save some cost if I go in this direction.