Oops, I guess I slightly misunderstood your question the first time. I'll try to clarify my answers:
What you're not answering is are the two channels separate or are they summed to mono when using a stereo to stereo instance?
The two input channels are not summed to mono when processing a stereo signal. Each channel of the stereo signal is processed separately (as a mono signal) within the plugin, and the processed results are passed to the two output channels, producing a stereo output. However, these two signal chains can be interconnected so that there is an interaction between the left and right channel.
Another way to think about it: each of the patch cables carries a mono signal, and each of the effects blocks processes a mono signal.
Also is there any interaction between the 2 channels when in stereo mode without having to route like you did?
I'm not 100% sure I understand this part of your question–it's definitely possible for the channels to interact with each other. I tried to create a relatively simple demonstration of this with the screenshot I posted, but there are also presets that ship with the plugin that do this out of the box.
The article linked to laments that there is no stereo linking.
Unfortunately I also don't speak German, but I think what the article means by "no stereo linking" is that, since the signal routing within the plugin is all mono, it requires twice as many effects blocks to perform the same effect on both channels. This is true.
Does that answer your questions?