Original scene was far from perfect, but it was somewhat more consistent: a sunny spring day, warm tones, noon, some sun rays casting deep shadows on the face (traditionally the worst time for outdoor portrait photography, hehe).

With "DLSS ON" it's something like an overcast sky; there are some flat shadows on the building in the background but the shadows on the building on the right are still just as sharp as before; the overall tone of the scene became colder; sun rays on clothes disappeared but there still deep shadows on man's face as if the sun was still shining from above, and the tone of his face is basically the same, despite the new color balance.

Edit: wrong, they are mentioned in the article and will support it themselves.