To my understanding, changing the virtual density would affect the contact angle because the increased / decreased density gradient with the gas increases / decreases the solid-gas surface energy. So the solid-liquid area changes to reduce the total surface energy. This therefore affects the contact angle in a similar way to changing the fluid-solid force, which may be sufficient depending upon what you are doing.
However, I don’t believe it truly models the interaction with the solid because this would require a Neumann boundary condition in the density rather than a Dirichlet condition. There is more detail about this in chapter 9 of ‘The Lattice Boltzmann Method: Principles and Practice’ if you are interested.
Apologies for the delayed response.