Miltek non resonated exhaust middle tip not being used?

So I recently installed a miltek non resonated exhuast and I love it.

It has three exhaust tips and I noticed that the middle tip is super clean compared to the two other tips on the end.

Is the exhuast defective or is there something I'm not understanding about the middle tip of the exhuast. Is it only used during boost??

The ens tips have your typical carbon build up, whereas the middle one still has a good shine to it, and very little to no carbon build up

I just watched the video of the exhaust and it's the same thing, middle exhaust is pretty damn clean, why is that??

I have the Remus and only the middle one has carbon build up. I have a feeling the outer two are more for the looks and while functional take a tiny % of the gases

I'd say the miltek is the same, but nothing to worry about

Edit: I have the valve open fully all the time I am not sure if it was closed may see the outer ones clog up. Still, you will get dominate airflow, like many golf Rs have dirtier pipes out of the 4

This is why it stays clean.