As you noticed, I was asking a question, which you ended up answering in a suitably passive-aggressive manner.
It has been possible to fit high end graphics cards into ITX-cases for a long time now... Allowing for better airflow is an interesting point but I think the the real enabler is the low TDP, resulting in less heat produced regardless of the size of the card.
Apologies, not my intention.
Cases are built to fit the components that go into them. Large GPUs require large spaces to contain them and still allow adequate airflow. If you wish to have a smaller, less intrusive case you have no choice but to compromise GPU performance. The Nano will allegedly give 290X - 980 performance with a far smaller footprint.
I personally see it as a step forward.