The problem that almost all current AI research has is that nobody knows if your model is detecting the obstacle or the absence of a road.
The cliché example is when people tried to build a tank classifier. Since they took the pictures of the different tank types on different days, the AI learned to detect the weather conditions instead.
So to determine if your AI is detecting the roads absence, you would first need a lot of testing images that look realistic in general, but with absent road. As far as I know, such a dataset does not publicly exist yet.
The cliché example is when people tried to build a tank classifier. Since they took the pictures of the different tank types on different days, the AI learned to detect the weather conditions instead.
So to determine if your AI is detecting the roads absence, you would first need a lot of testing images that look realistic in general, but with absent road. As far as I know, such a dataset does not publicly exist yet.
So yes, that commenters approach seems new to me.