By citing to examples where it's done correctly the article gives the impression that writing unfilmables is almost never a bad idea. "Just don't overdo it."
The problem is that far too often inexperienced writers will put into their scene descriptions information that is critical to the scene and the narrative as a whole but which if shot and presented would not be understood by the audience. They are confusing the general form of the novel with screenwriting. If it's written in there somewhere, it exists in the story.
This just isn't the case with screenwriting. If it isn't presented visually, dramatically within the scene it doesn't exist in the story. The descriptions in the sample scenes don't contain information important to those scenes.
Just because something is a "character piece" doesn't mean it's a well executed character piece. The vast majority who those ever sit at their computers to write a screenplay fundamentally don't understand drama, conflict, and tension. That's more or less what is meant by "don't be boring".