This is a nomenclature issue. But as a non-involved person, the key function of a virus is distribution/virulance. Gain of Function means increasing the effectiveness of the key function. So making a virus spread more, making an immune cell more effective against pathogens, making a retina cell more sensitive to light.

Gaining An Additional Function is not the same thing, although the confusion is understandable.

Understood, thanks for nicely explaining it instead of downvoting ;)