You're talking about two different issues now.
The tips being disconnected has nothing to do with why one is dirty and one is clean.
The Golf R has 4 exits and 4 tips. The tips are detached, as are many cars these days. 2 of the exits are valved and so only flow exhaust gas when opened in sport mode, hence only 2 getting dirty normally.
But that's just more fakery. The one on the right is the functional one which goes directly to the back box. The one with the baffle is just linked to the side of that but has a longer path, so even when open most of the gasses would escape through the one on the right. All it will do is change the noise.