Definitely some sharpening but I wouldn’t say that it looks better. Observe the haloing at the edge of the rock face and the noisiness of the water. IV’s render is above the dotted line and RT’s below.
As well, something is amiss with the colors. The fact that IV and the default viewer don’t have as many color management options tells me that they likely aren’t as robust in color as RT. (I mentioned app themes because the colors of the surrounding area also affect how we perceive the image.)
Anyway, color management and perception is a very complicated matter. Just observe how much head scratching is being done in Monitor profiles and deep shadow tonality. Try comparing the thread’s train track and squares images in IV and RT.